Prime Minister Theresa May said she would chair a meeting of the Cobra emergency committee later Monday. She said there has been no conflict among the groups in the past.
A police forensic tent erected at the scene in Finsbury Park, after a van collided with pedestrians.
The Metropolitan Police said eight people were taken to hospital and several were seriously injured in the incident which occurred on Seven Sisters Road after 12.20am.
One eyewitness who lives nearby told the BBC she saw people "shouting and screaming".
"Extra officers are on duty in the area to help reassure the local community", Police Commissioner Cressida Dick said.
Turkish troops hold exercises in Qatar in show of support
Prior to the diplomatic row, Qatari nationals could travel visa-free between Saudi Arabia, the UAE, Kuwait, Oman and Bahrain. The channel posted a video on its website of a column of armoured personnel carriers moving through streets.
Another witness, Hussain Ali, 28, said that while being restrained the suspect was protected by the people he is thought to have been targeting.
A witness, 38-year-old worshipper named Mehdi, told the Evening Standard that the van "tried to do a London Bridge thing", referring to the June 3 incident in which three male attackers deliberately crashed their van into pedestrians on the London Bridge. Rudd, who is in charge of government law enforcement, said: "Londoners have been hit with a series of attacksand have been nothing short of heroic". "In the meantime, I call on everyone to stand together against those who seek to divide us".
The Finsbury Park mosque has been associated with hate preacher Abu Hamza and a number of terrorists including shoebomber Richard Reid who attempted to detonate explosives on a flight from Paris to Miami in 2001.
Labour leader Jeremy Corbyn tweeted: "I'm totally shocked at the incident at Finsbury Park tonight".
"From the window, I started hearing a lot of yelling and screeching, a lot of chaos outside".
Police have not yet determined whether the fatality was a result of the van attack.
Van hits pedestrians in London; 'number of casualties' reported
London Mayor Sadiq Khan urged people to "remain calm and vigilant" after the " horrific terrorist attack on innocent people ". Amber Rudd, the Home Secretary, said her "thoughts are with all those affected by the appalling incident at Finsbury Park".
Speaking to Buzzfeed News, he said: "This big van just came and went all over us".
Police have not offered any details about the cause of the crash. "I want to kill all Muslims".
He said he was also concerned about the lack of security measures around the building, and that congregations leaving prayers were not advised the safe way to enter and exit the mosque.
At this early stage of this investigation, no other suspects at the scene have been identified or reported to police, however the investigation continues. The Muslim Council of Britain has called the incident in London where a vehicle hit pedestrians earlier on Monday the most violent manifestation of Islamophobia to date.
However it is not known if the man's death is directly related to the attack, as he was already receiving first aid from the public at the scene.
On March 22, a man killed five people when he drove a auto into pedestrians on Westminster Bridge in London and stabbed a police officer.
Special counsel investigating business dealings of Jared Kushner
The Post reported on Wednesday that Mueller was investigating Trump to prove whether the president attempted to obstruct justice. Kushner previously volunteered to share with Congress what he knows about Russia-related matters".
In May, 22 people were killed in an explosion at an Ariana Grande concert at the Manchester Arena.
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