One man dead, 10 injured after van hits pedestrians outside London mosque, man arrested

A man has been killed and 10 people injured after a van was driven into a crowd of worshippers outside a mosque in a suspected revenge attack in London's north.

Police arrested a man at the scene with a witness saying he leapt out of the van and shouted that he wanted to "kill all Muslims".

Police said they were called to the scene outside Muslim Welfare House, near the Finsbury Park Mosque on Seven Sisters Road north of London, at 12.20am on Monday morning.

A man was pronounced dead at the scene, eight were injured and taken to three hospitals with two others treated for minor injuries at the scene.

Two of those taken to hospital are in serious condition, according to police.

A 48-year-old man was detained by members of the public after he ran from the van and he was then arrested by police.

Witnesses at the scene claim the man laughed, blew kisses at horrified onlookers and said "I did my bit" before being wrestled to the ground.

London’s Metropolitan Police have now described the incident as a terrorist attack.

"He has been taken to hospital as a precaution, and will be taken into custody once discharged," London police said in a statement.

"He will also be subject of a mental health assessment in due course.

Witnesses said the white hire van deliberately swerved off the road and ploughed into the crowd of people, The London Evening Standard reports.

UK Prime Minister Theresa May has described the attack as "sickening" in an address outside her Downing Street residence.

"This was an attack on Muslims near their place of worship and like all terrorism, in whatever form, it shares the same fundamental goal - it seeks to drive us apart," she said.

"There has been far too much tolerance of extremism, including Islamophobia," she said.

Horrific footage posted on social media has captured the chaotic moments after the incident including including bleeding and injured people lying on the ground.

Videos shared on Twitter appear to show the arrest of one man, suspected to be the driver of the van.

Despite some media reports, police said they could not confirm anyone had been stabbed.

A number of Muslim worshippers were said to be breaking their fast at a café having attended Tarawih prayers, performed for the Islamic holy month of Ramadan.

The incident occurred in the vicinity of the Finsbury Park Mosque and the nearby railway station.

The Muslim Council of Britain said on Twitter a van struck a number of worshippers as they left the mosque, adding, "Our prayers are with the victims."

Mohammed Kozbar, chairman of the mosque, told The Sun: "Whoever did this, he did it to hurt people and it's a terrorist attack.

"We call it a terrorist attack as we called it in Manchester, Westminster and London Bridge."

A witness told Reuters they saw at least one person being loaded into the back of an ambulance.

A number of witnesses described the scene on Twitter.

"Horrible to watch police officers doing cardiac massage at people on the floor, desperately trying to save them. I just hope they did," Cynthia Vanzella said.

The incident follows a series of attacks in Britain.

Eight people were killed and 50 injured on June 3 when three Islamist militants drove into pedestrians on London Bridge and stabbed people at nearby restaurants and bars.

On March 22, a man drove a rented car into pedestrians on Westminster Bridge in London and stabbed a policeman to death before being shot dead. His attack killed five people.

On May 22, a suicide bomber killed 22 people at a concert by American pop singer Ariana Grande in Manchester in northern England.

• With AAP & Reuters