At least one person has been confirmed killed and 10 others injured after a van allegedly rammed into a crowd of pedestrians near a mosque in north London early on Monday morning (local time).
UK Prime Minister Theresa May said police are treating the incident on Seven Sisters Rd, near Finsbury Park, as a "potential terrorist attack".
One man has been arrested, but witnesses report another two men escaped from the van after the crash and are still at large. Police are investigating whether other people are involved.
A witness told BuzzFeed News the man driving the van was yelling "I want to kill all Muslims" during the crash.
Metropolitan Police have confirmed one man died at the scene, while eight people were taken to hospital and two others were treated at the scene for minor injuries.
Police also denied reports people had been stabbed during the incident, saying: "At this stage there are no reports of any persons having suffered any knife injuries."
The Muslim Council of Britain said the crash was outside the Muslim Welfare House, which is about 300m away from the Finsbury Park Mosque.
It's believed worshippers leaving the mosque after late-night prayers may have been targeted in the attack.
The ramming came during the Muslim holy month of Ramadan, when people attend prayers at night.
"Of course it is a terrorist attack, this is a terrorist attack," eyewitness Mohammed Abdullah said.
"This is something he's done on purpose. They did it on purpose. They've done it exactly after the hour of prayer."
Police have yet to confirm whether the crash was intentional, but Huran Khan, secretary-general of the Muslim Council, believes it was.
"I am shocked and outraged to hear a van has intentionally run over worshippers leaving Ramadan night prayers on Seven Sisters Rd Finsbury Park," he said.
Assistant secretary general Miqdaad Versi told Reuters the van swerved into a group of people who were helping an unwell man who had fallen into the ground.
"A number of passers-by, or friends, or people who had come by from the mosque, were gathering around him to help take him to his family, take him to his house," he said.
"At that moment in time, basically a van swerved into them deliberately."
The Counter-Terrorism unit is investigating the crash.
Ms May issued a statement saying her thoughts are with those who have been injured.
"This is a terrible incident. All my thoughts are with those who have been injured, their loved ones, and the emergency services on the scene," she said.