MCB deputy head Miqdaad Versi said the incident happened “outside the Muslim Welfare House”, which is on Seven Sisters Road near the mosque.
The Metropolitan Police called the event “a major incident” and said one person had been killed and 10 were injured.
Last month seven people had died in a terrorist attack at London Bridge.
Police said they had deployed extra policing resources “to reassure communities, especially those observing Ramadan”. An AFP reporter could see a helicopter and several emergency vehicles at the scene, which was closed off by a wide police cordon. “They were all leaving the mosque when they got hit”.
He was detained by the crowd at the scene until police arrived.
Its former imam, Abu Hamza, was jailed in Britain for inciting violence and racial hatred before being extradited to NY, where he was sentenced to life in prison for terrorism in 2015.
The mosque was raided by authorities in January 2003, and in February 2005, it was completely reconstituted – “run by a new board of trustees with a new management team, new imams, a new name and new ethos”, according to its website.
The incident occurred in Finsbury Park, a neighborhood in north London where many immigrants live.
Eyewitnesses said there were a total of three “attackers”, one of whom was apprehended while two more fled the scene.
The incident comes at a time of political turmoil in Britain, as Prime Minister Theresa May plunges into divorce talks with the European Union weakened by the loss of her parliamentary majority in a June 8 election.
Labour leader Jeremy Corbyn said he was “totally shocked by the incident”.
On March 22, a man drove a rented vehicle into pedestrians on Westminster Bridge in London and stabbed a policeman to death before being shot dead.
London Mayor Sadiq Khan called the incident “a horrific terrorist attack” and said “this was clearly a deliberate attack on innocent Londoners”. Eight people were killed before the men were shot to death by police.