Venezuela, a top oil exporter in deep crisis

Benchmark crude prices tumbled almost $3 per barrel in London and fell more than $2 in New York

Latin America's top oil exporter, Venezuela, is deep in an economic and political crisis brought on plummeting oil prices and marked by violent anti-government protests.

Ahead of presidential elections on Sunday, in which Nicolas Maduro is seeking a second term, here is some essential background.

- Hard times for Chavez heir -

Maduro was propelled into power in 2013 at the death of the hugely popular Hugo Chavez, who designated his then vice president as his political heir.

They were big shoes to fill, and Maduro has struggled.

Chavez, first elected in 1999, mixed a larger-than-life personality with a man-of-the-people style, his popularity underpinned by oil-funded social programs.

But Maduro quickly lost favor. Despite leaning on the symbols and rhetoric of Chavism, he lacked the charisma of his predecessor and suffered when a fall in oil prices in 2014 lead to an economic crisis.

The crisis provoked anti-government riots that raged for months in 2014, with the authorities reacting with force. Forty-three people were killed.

In 2017, protests calling for Maduro to step down lasted for four months, leaving 125 people dead.

- All about oil -

The South American nation has the largest proven oil reserves in the world, estimated at around 302 billion barrels.

It is almost totally dependent on its black gold production, which accounts for 96 percent of exports and half of state revenue.

However, in April the IMF said Venezuela's crude production had dropped by half in the past 18 months. Lack of investment in infrastructure has been blamed for the collapse.

The United States -- with whom Venezuela has strained ties -- is its biggest customer for oil, with about a third of production also going to China and Russia and used to pay off debts.

- Economy in free fall -

Home to 30 million people, the country's economy has been shrinking since 2014.

In the past five years, the GDP has declined by 45 percent according to the IMF, which has forecast a further contraction of 13 percent in 2018.

The IMF said in April that Venezuela's economic collapse ranked as one of the worst in modern history.

Inflation reached 13,779 percent in 2017, according to a study released this month by the opposition-dominated National Assembly. It confirmed other estimates that Venezuela has the world's highest inflation rate.

- Running on empty -

In partial default on its debt, Venezuela also suffers severe shortages of food and medicines, with about 80 percent of treatments lacking, according to the Venezuelan Pharmaceutical Federation.

Government statistics say around 23 percent of the population lives in poverty -- but a study by the country's main universities put the figure at 87 percent for last year. Electricity blackouts and water shortages are frequent.

The worsening situation has seen nearly a million Venezuelans leave the country over the past two years, according to the International Organization for Migration.

Many head to Brazil, Colombia and Panama, and often beyond.

Venezuela also suffers from endemic violence -- its homicide rate in 2017 was 89 per 100,000 inhabitants, according to the Venezuelan Violence Observatory.

Venezuela is almost totally dependent on its oil production, which accounts for 96 percent of exports and half of state revenue