A man has died and eight people have been injured after a van drove into pedestrians near Finsbury Park mosque in Seven Sisters Road, London.
A 48-year-old man has been arrested and Prime Minister Theresa May said police were treating it as a "potential terrorist attack". She will chair an emergency meeting later.
Many of the victims are believed to have just left evening prayers at the Muslim Welfare House after breaking the Ramadan fast.
In a statement, The Metropolitan Police said: "Met Police were called just after 0020hrs to reports of a vehicle in collision with pedestrians. Officers attended alongside other emergency services and found and tended to a number of casualties.
"One man was pronounced dead at the scene. Officers are in the process of informing next of kin. A post mortem examination will be scheduled due course.
"Eight people injured were taken to three separate hospitals; two people were treated at the scene for minor injuries."
The police said it an investigation of the incident is being carried out by the counter terrorism command.
"Due to the nature of this incident extra policing resources have been deployed in order to reassure communities, especially those observing Ramadan," the police added.
Large sections of Seven Sisters Road were closed following the incident.
London Ambulance Service said: "We have sent a number of resources to an incident in Seven Sisters Road."
Whatever it was it's over with just so many police flooding the area. pic.twitter.com/HzMRigpPYr— ben tovey (@ben_tovey) June 18, 2017
Seven Sisters Road has been closed northbound between Hornsey Road and Rock Street, Transport for London tweeted.
The Muslim Council of Britain tweeted: “We have been informed that a van has run over worshippers as they left #FinsburyPark Mosque. Our prayers are with the victims.”
Mayor of London Sadiq Khan said:
The Metropolitan Police are responding to a horrific terrorist attack on innocent people in Finsbury Park.
My thoughts and prayers are with everyone affected. I am grateful to our emergency services, who responded quickly and have been working on the scene throughout the night.
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.
While this appears to be an attack on a particular community, like the terrible attacks in Manchester, Westminster and London Bridge it is also an assault on all our shared values of tolerance, freedom and respect.
Home secretary Amber Rudd called it an "appalling incident".
"We must all continue to stand together, resolute, against all those who try to divide us and spread hate and fear," she said.