May condemned the assault as "sickening", saying Britain's determination to fight "terrorism, extremism and hatred... must be the same, whoever is responsible".
Many locals lingered until mid-morning by the cordoned off scene, shocked not only that yet another apparent terror attack had hit Britain, but that it appeared to have targeted Britain's Muslim community.
"This was quite clearly an attack on Muslims who looked like they were probably Muslims and they were coming from a prayer meeting", said the Met police commissioner, Cressida Dick.
In a statement outside her Downing Street office, British Prime Minister Theresa May promised extra police resources would be deployed to provide reassurance and said Britain had been far too tolerant of all forms of extremism in the past. The two men murdered on the Portland train died defending a Muslim woman from a White supremacist. "Diverse, welcoming, vibrant, compassionate, confident and determined never to give in to hate", she said in her statement.
"Leave Our Muslim Neighbours Alone", said a placard held up by Alison, who told AFP that she was "upset and angry that my neighbourhood has been defiled by these people who are racists and idiots".
"We told them the situation - theres a man, hes restrained, he mowed down a group of people with his van and there is a mob attempting to hurt him and if you dont take him then, God forbid, he might be seriously hurt".
But Kacimi said there was no need for the community to panic, because police and government officials have been "very, very supportive".
Opened in 1994, Finsbury Park Mosque is an unassuming five-story redbrick building in residential north London, close to Arsenal Football Club's Emirates Stadium.
British security officials, speaking on condition of anonymity in line with official policy, said hate crimes directed at Muslims have increased almost five-fold in the wake of several attacks in Britain. These are the values that define this city, "she said".
At a press conference on Monday, Mayor of LondonSadiq Khan was asked by a reporter if the threat from Islamophobia has been "underestimated".
He added that it had "all the hallmarks" of a terrorist attack. Basu said it was a "challenging" time for London and that the emergency services were stretched.
Then on June 3, eight people were killed and 48 were injured when three men drove a van into pedestrians on London Bridge before leaping out and launching a stabbing spree in nearby bars and restaurants. Reports indicate that the people inside of the Finsbury Park mosque who were hit had just broken their fast.
"When I looked back, I thought it was a vehicle accident, but people were shouting, screaming and I realized this was a man choosing to terrorize people who are praying, an eye witness told Reuters".
He said: "An attack on a mosque, an attack on a synagogue, an attack on a church, is actually an attack on all of us".
The person spoke on condition of anonymity because he was not authorized to speak about the ongoing investigation into an attack on worshippers outside a mosque in London.
"At this stage, we are calling for calm", he said.
It also follows a suicide bombing at a pop concert in Manchester, northern England, in May which killed 22, while in March, a man drove a rented auto into pedestrians on Westminster Bridge in London and stabbed a policeman to death before being shot dead.
On May 22, a suicide bomber killed 22 people at a concert by American pop singer Ariana Grande in Manchester in northern England.