One person was killed and eight others were injured early Monday when a van struck worshippers near a North London mosque, in an incident police are treating as a "potential terrorist attack."
Police said they responded to a "major incident," after reports shortly after midnight of a vehicle colliding with pedestrians in Seven Sisters Road.
There were a number of casualties at the scene and a 48-year-old man was arrested after being detained by a member of the public, police said.
Authorities have not yet confirmed if the event was a deliberate act or a terrorist incident, however Prime Minister Theresa May said police were treating it as a "potential terrorist attack."
May described the event as a "terrible incident," and added "all my thoughts are with those who have been injured, their loved ones and the emergency services on the scene."
London mayor Sadiq Khan labelled the incident a "horrific terrorist attack on innocent people."
"We don't yet know the full details, but this was clearly a deliberate attack on innocent Londoners, many of whom were finishing prayers during the holy month of Ramadan," Khan said in a statement.
The suspect screamed "I'm going to kill all Muslims," according to witness Abdulrahman Saleh Alamoudi who was assisting victims.
Eight people were taken to hospital and a number of others were treated at the scene for minor injuries, the London Ambulance service said.
Witnesses said a van veered off the road into crowds outside Finsbury Park mosque, the Independent newspaper reported.
The Muslim Council of Britain condemned the incident as a "terror attack on worshippers leaving prayers," and called for security at mosques to be increased.
"It appears from eyewitness accounts that the perpetrator was motivated by Islamophobia," the Council's secretary general Harun Khan said in a statement published on Twitter.
The Council also clarified that the incident took place outside the Muslim Welfare House, 300 metres away from the mosque.
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.
"The gentleman went straight down this road, people were just conversing, talking, just doing what we're doing. And he just came into all of us," an unnamed local resident told the Press Association.
"There were bodies around me. Thank God I just moved to the side, I just jumped," the witness added.
Footage showed injured people lying on the ground and angry crowds surrounding a man believed to be the driver of the vehicle, according to the Independent.
"Horrible to watch police officers doing cardiac massage at people on the floor, desperately trying to save them. I just hope they did," witness Cynthia Vanzella wrote on Twitter.
The incident comes towards the end of Ramadan, the holiest time of year for Muslims.
Britain's terrorist alert level is currently at "severe" meaning an attack is highly likely.
Earlier this month, three men who pledged allegiance to the Islamic State terrorist organization, rammed a van into pedestrians on London Bridge before stabbing passers-by, killing eight.
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