In a speech last week, a former police chief warned that anti-Muslim sentiment online has been "relentless" following the London Bridge attack on June 3.
The van ploughed through a crowd outside the north London mosque at about 12.20am on Monday, injuring 10 people and leaving an elderly man who suffered a heart attack dead.
Police declared it a terrorist incident within eight minutes, May said.
Prime Minister Theresa May will chair an emergency meeting on Monday morning.
"This was an attack on Muslims near their place of worship".
London police closed the area to normal traffic. Police said a man who was driving the auto has been arrested and taken to a. "The police could not confirm... if they... passed away or [had] been taken to hospital".
Sky News reported that the mosque's imam, Mohammed Mahmoud, prevented the crowd from beating the attacker, aged 48, until police arrived and arrested him on suspicion of attempted murder.
- The incident unfolded as evening Ramadan prayers ended.
Talking to reporters outside 10 Downing Street, she said people have come together to condemn the act like they have done before. "Extra officers are on duty in the area to help reassure the local community", she said.
The counter-terrorism command is leading the investigation, officials said.
Mak Chishty, an ex-Metropolitan Police commander who had been the country's most senior Muslim officer before his retirement, said: "The backlash has been something of a different scale".
Pakistan's path to Champions Trophy glory
He didn't have any control on the ball and Pakistani batsmen, specially Fakhar Zaman went after him on nearly every delivery. Put in to bat, Pakistan rode on a century by opener Fakhar Zaman to post a massive total of 338/4 in the allotted 50 overs.
Basu confirmed witness accounts that the man found dead at the scene was already receiving first aid when the attack happened, adding it was unclear whether he died as a result of the attack. Two of them are seriously injured.
Warfa said numerous people in the street were worshipers who'd been attending late-night Taraweeh prayers at Finsbury Park Mosque. The mosque itself gained notoriety more than a decade ago for sermons by radical cleric Abu Hamza al-Masri, who was sentenced to life in a USA prison in January 2015 after being convicted of terrorism-related charges.
Hamza was later extradited to the United States and jailed for life there in 2015 for playing a key role in the 1998 kidnapping of 16 Western tourists in Yemen, four of whom were killed, and in trying to set up a USA terror training camp in 1999.
- Since then, the mosque has worked to turn its reputation around and now operates mostly as a community center. The mosque called it a "callous terrorist attack". The group's general secretary, Harun Khan, described the incident as a hate crime against Muslims.
London Mayor Sadiq Khan denounced the incident as a "horrific terrorist attack".
"Today's attack falls at a hard time in the life of this city, following on from the attack on London Bridge two weeks ago - and of course the unimaginable tragedy of Grenfell Tower last week", May said.
"The British Muslim community requires all decent people to stand with us against this evil violence".
We must all be builders of understanding, compassion and peace, day by day, in our homes, our work and our communities. Muslim leaders called for calm.
Meanwhile, the Muslim Council of Britain described the incident as "the most violent manifestation of Islamophobia in Britain in recent months". "During the night, ordinary British citizens were set upon while they were going about their lives, completing their night worship".
The council tweeted that its prayers were with the victims.
The attack comes during the Muslim holy month of Ramadan when Muslims were attending special prayers.
Comments