G20 LIVE: Rolling coverage

US President Barack Obama has brought the G20 summit to life with an inspiring speech to around two thousand people at the University of Queensland.

Mr Obama used his Brisbane address to announce the United States will pump $US3 billion ($A3.3 billion) into a global climate fund, stepping up pressure on other nations such as Australia to follow suit.

"No nation is immune and every nation must play its part," he said.

"We can get this done."

The United Nations Green Climate Fund, was set up to support developing nations dealing with the impacts of climate change, such as rising seas, higher temperatures and extreme weather.

The US contribution is the biggest country pledge so far.

The UN will now have about $US6 billion of the $US10 billion it hopes to raise.

The announcement at the University of Queensland was made in an auditorium partly powered by a solar array.

Mr Obama used Australia as an example of what could happen if climate change wasn't addressed.

"Here, a climate that increases in temperature will mean more extreme and frequent storms, more flooding, rising seas that submerge Pacific Islands.

"Here in Australia it means longer droughts, more wildfires. The incredible natural glory of the Great Barrier Reef is threatened."

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Australia, which holds the current G20 presidency, declined to put climate change on the official 2014 agenda.

However, the historic deal by China and the US has all but guaranteed it should be a G20 talking point at leaders' meeting in Brisbane, which started on Saturday.

"If China and the US can agree on this, then the world can agree on this - we can get this done and it is necessary for us to get it done,” Mr Obama said.

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G20 LIVE: Here's how the rest of the day unfolded:

UPDATE 6.10pm (AEST)

World leaders have released a statement addressing the Ebola outbreak in West Africa.

"We are deeply concerned about the Ebola outbreak in Guinea, Liberia and Sierra Leone and saddened by the suffering and loss of life it is inflicting. We are mindful of the serious humanitarian, social and economic impacts on those countries, and of the potential for these impacts to spread."

Earlier today, protesters marched in Brisbane calling for world leaders to take greater action to fight the crisis.

UPDATE 5.30pm (AEST)

World leaders have finished their sit-down meeting at the Brisbane Convention and Exhibition Centre.

They are now gathering for an official 'family' photo.

UPDATE 5.00m (AEST)

Police have held a briefing to discuss their activities at the G20 summit on Saturday.

UPDATE 4.40pm (AEST)

A woman has been been charged with possessing a prohibited item after she was found carrying a gas mask during G20 demonstrations.

She was arrested by police while protesting near Roma Street earlier today.

The 25-year-old is due to appear in court next month

UPDATE 3.45 pm (AEST)

Prime Minister Tony Abbott is making the opening remarks at the G20 summit.

"As you look around the world, there are many difficulties and problems, there are problems in the Middle East and there are problems in eastern Europe and there are terrible problems in West Africa."

"Growth has been fragile but the message that should come from us over these next two days is a message of hope and optimism.

"Yes, our world can grow and, yes, our world can deliver the jobs that our people want.

"We believe that, as a result of the work that we will do, the world can grow by more than 2 per cent more over the next five years than would otherwise be the case.

"Governments can deliver, that Governments can agree that the world can be better, that there can be higher jobs, higher growth and more jobs, that is the message that I want to go forward from these two days. That is what the world expects of us. They want more growth."

Leaders are now seated and will begin official talks, which are expected to last for an hour and a half.

UPDATE 3.30pm (AEST)

World leaders are attending the 'Welcome to Country' ceremony after arriving at the Brisbane Convention and Exhibition Centre.

UPDATE 3.20pm (AEST)

Ciaron O'Reilly has been arrested during demonstrations near Musgrave Park this afternoon.

O'Reiley describes himself as a non-violent anti-war protester but he was one of the activists prohibited from the G20 zone after spending several months in jail in the United States for breaking into a military base in New York.

UPDATE 3.10pm (AEST)

Motorcades have begun arriving at the Brisbane Convention and Exhibition Centre ahead of the official start of the G20 summit in Brisbane.

The Prime Minister is formally greeting world leaders as they arrive, in front of a swarm of media.

Earlier, world leaders attended a lavish seafood BBQ at Queensland Parliament House.

The luncheon was a chance for dignitaries to mix informally before sitting down for official talks.

The traditional Aussie dessert, pavlova, was served for dessert.

UPDATE 2.20pm (AEST)

Hundreds of people have staged a powerful anti-Putin march in Brisbane, calling for Russian President Vladimir Putin to be excluded from the G20.

Protesters say they believe Russia was involved in the downing of fight MH17.

Ukrainians and Australians laid coffins in memory of the victims of the tragedy, with demonstrators chanting 'Putin get out.'

Meanwhile, about 40 pro-Russian demonstrators are also rallying at Brisbane's South Bank in support of Mr Putin.

They say they were devastated by the downing of flight MH17 but feel alienated by Tony Abbott's shirt-front remarks.

UPDATE 1.55pm (AEST)

Barack Obama has received a standing ovation at the end of his historic speech at the University of Queensland.

In concluding, Mr Obama said he wanted to continue to build a strong relationship with Australia.

"We want to be your partner because we believe in the leaders you can be and the difference you can make to ignite positive change and when you succeed the world will be a little more free," he said.

"So that's the future we can build together.

"And in pursuit of that future you will have no greater friend than the United States of America. So thanks very much, God bless Australia, God bless America, God bless our great alliance. Thank you."

UPDATE 1.10pm (AEST)

The US President has arrived at the University of Queensland and has begun his landmark address.

• WATCH BARACK OBAMA'S LANDMARK SPEECH

UPDATE 12.50pm (AEST)

US President Barack Obama has left Queensland Parliament House and is making his way towards the University of Queensland, where he is due to make an historic address.

UPDATE 12.45pm (AEST)

An anti-Putin protest has begun in Brisbane's CBD.

Demonstrators are angry at the Russian government's handling of the MH17 tragedy, which claimed the lives of dozens of Australian citizens and residents.

UPDATE 12.40pm (AEST)

UPDATE 12.20pm (AEST)

Two people have been arrested after police found gas masks in their bags.

There are also reports a knife was found in one of their bags.

The women were taken to police headquarters where they are being questioned by police.

Authorities have banned a number of items from the G20 red zone, including those allegedly found on the demonstrators.

UPDATE 11.15am (AEST)

Prime Minister Tony Abbott is welcoming world leaders at the Leader's Retreat at Queensland Parliament House.

Delegates from 19 countries and the European Union are attending the three-day event, representing 19 of the world's major and emerging economies.

A large focus of the summit is to address the world's growth challenge, with members aiming to add an extra two trillion dollars to global GDP.

UPDATE 11.00am (AEST)

The countdown is on to US President Barack Obama's landmark speech at the University of Queensland this afternoon.

He will address audiences around 1pm (AEST) before attending the G20 summit.

Mr Obama is set to discuss US leadership in the Asia-Pacific region.

Security has been stepped up in preparation for the President's visit, with the campus in lock down since Friday.

UPDATE 10.45am (AEST)

The United Nations Secretary General Ban Ki-moon is speaking at the G20 summit.

He is discussing the biggest issues facing world leaders and calling for greater action to address challenges.

• SEE BAN KI-MOON's FULL SPEECH

UPDATE 10.30am (AEST0

Spouses have begun arriving at Lone Pine where they'll meet with the wives of other world leaders in Brisbane for the G20 summit.

UPDATE 10.25am (AEST)

US President Barack Obama has arrived in his 'Beast' at Queensland Parliment House.

The gates of Parliament have now been locked, with all world leaders inside for the Leader's Retreat.

UPDATE 10.10am (AEST)

Here is a list of the main protests scheduled for Saturday:

-9am: Ebola- Aid workers want to persuade leaders to do more to stop the disease's spread

-11am: Pro-capitalism - Australian Taxpayers' Alliance lead a rally at South Bank in support of free trade and markets

-11am: People's March - Rally and march across the CBD against G20 "for the environment, democracy and justice"

-11am: Anonymous - The hacktivist group will rally at Roma Street Parkland

-12pm: Asylum Seekers - 1000 paper boats will be launched on the Brisbane River near South Bank to highlight the plight of asylum seekers

-1.30pm: Protest Against Putin - Rally at King George Square to urge G20 leaders to stand up to the Russian president

UPDATE 9.40am (AEST)

Police are preparing for US President Barack Obama to leave the Marriott Hotel in the CBD, on his way to the Leader's Retreat at Queensland Parliament House.

UPDATE 9.30am (AEST)

UPDATE 9.00am (AEST)

World leaders are leaving their hotels and traveling to Queensland Parliament House for the Leader's retreat.

The retreat is essentially a way to 'break the ice' ahead of the formal proceedings at the G20 summit.

Trade and infrastructure are at the top of the agenda on the first day of the G20.

UPDATE 8.20am (AEST)

UPDATE 8.10am (AEST)

UPDATE 7.30am (AEST)

French President François Hollande has touched down in Brisbane for the G20 summit.

He is one of the last world leaders to arrive.

UPDATE 6.30am (AEST)

US President Barack Obama has thrilled an excited crowd of spectators, giving them a wave as he arrived at the Brisbane hotel where he'll be staying for the G20 summit.

About 100 people gathered at the Marriott Hotel on the Brisbane River to catch a glimpse of the president's impressive motorcade, which included two of his bullet-proof limousines, a dozen other vehicles and seven motorbikes.

The motorcade brought traffic to a standstill as it travelled to the hotel from Victoria Park at Herston, where the president arrived in the presidential helicopter Marine One.

A small but excited crowd gathered at the hotel to watch the arrival, and as the president arrived in his limousine, dubbed The Beast, he gave a small wave to those assembled there, as choppers buzzed overhead.

Others did their best to catch a glimpse from the balconies of neighbouring highrise buildings.

Earlier, Air Force One touched down at the Amberley air force base west of Brisbane, with Governor-General Peter Cosgrove, Attorney-General George Brandis and Queensland Premier Campbell Newman there to greet the president.

Just before the president touched down, Italian prime minister Matteo Renzi and his wife also arrived for the summit of world leaders, which officially gets underway on Saturday.

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