A van plowed into worshippers near a London mosque in the early hours of Monday, injuring 11 people, two of them seriously, in what Prime Minister Theresa May said was a sickening, terrorist attack on Muslims.

The vehicle swerved into a group of mainly North and West African people shortly after midnight as they left prayers at the Muslim Welfare House and the nearby Finsbury Park Mosque in north London, one of the biggest in Britain.

The driver, a 47-year-old white man, was grabbed at the scene by locals and pinned down until police arrived.

The man was not named by police but local media reported he was a father of four who lived in Wales. He was held on suspicion of attempted murder which was later extended to preparing or instigating terrorism, including murder and attempted murder.

After being seized, he said he had wanted to kill "many Muslim people", one witness told journalists.

A man, who had earlier suffered a heart attack, died at the scene but it was not clear if his death was connected to the van attack.

"This morning, our country woke to news of another terrorist attack on the streets of our capital city: the second this month and every bit as sickening as those which have come before," May told reporters outside her Downing Street office.

"This was an attack on Muslims near their place of worship," said May who later visited the mosque.

The White House said U.S. President Donald Trump was receiving regular updates on the attack. "We've made it very clear to our British allies that we stand ready to provide any support and assistance that they may need," White House spokesman Sean Spicer told reporters at a briefing.

The attack was the fourth since March in Britain and the third to involve a vehicle deliberately driven at pedestrians.

It came at a tumultuous time for the government with Britain starting complex divorce talks with the European Union and May negotiating with a small Northern Irish party to stay in power after losing her parliamentary majority in a snap election that backfired.

When Muslims are victims: @DailyMail covers #FinsburyPark in context of being a 'revenge attack' which justifies targeting innocent people.

When #Muslims are continuously vilified in the media to the point where hate speech is normalised, acts of violence should be expected.