At least one person is dead, and eight are in hospital after a van slammed into crowds of pedestrians in Finsbury Park, north London, just after midnight on Monday morning local time.
A 48-year-old male suspect was arrested at the scene, according to London Metropolitan police, who said the investigation into the incident was ongoing.
-- One man pronounced dead at scene, police say.
-- Driver was detained by members of public at the scene before police arrived.
-- Investigation of the incident is being carried out by the Counter Terrorism Command.
-- Muslim Council of Britain releases a statement calling it a "terror attack."
Islington's Seven Sisters Road, where the incident took place, is home to at least four mosques, and would have likely been filled with worshipers leaving late-night taraweeh prayers and heading back toward the Finsbury Park Underground Station.
A statement released by the Muslim Council of Britain (MCB) condemned what it described as a "terror attack."
"During the night, ordinary British citizens were set upon while they were going about their lives, completing their night worship. My prayers are with the victims and their families," read the statement.
The Islington borough of North London, of which Finsbury Park is a part, is home to a large Muslim community. Around 10% of the borough's population is Muslim.
According to a tweet from Transport for London, Seven Sisters Road has been closed northbound at Hornsey Road and southbound at Rock Street.
The London Ambulance service said in a tweet that "a number of resources have been sent to an incident in Seven Sisters Road."
The incident comes at a time when emotions are high in England, where there have been several recent terrorist attacks in recent weeks.
On May 22, a suicide attack killed 22 people and injured nearly 60 after an Ariana Grande concert in Manchester.
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.
CNN national terror analyst Peter Bergen said the Finsbury Park neighborhood has a large Muslim population and the nearby mosque had a notorious reputation as a place where Islamist militants used to gather.
"If you were interested in targeting a group of Muslims at a mosque that was notorious, this would be the mosque you would do it at. I think it's significant that they had the reputation historically of being one of the most militant mosques in London. And that reputation may be more historical than current," he said.
Bergen added: "Ramadan, particularly in a country like the UK, where the days are very long in June, you know you're fasting from dawn to dusk and you're breaking the fast at night. ... Night comes pretty late in London this time of year. It wouldn't be odd that you would have large numbers of people breaking their fasts and praying at this time."
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. The mosque, which today operates largely as a community center, rose to international notoriety in the early 2000s, due to its links with Egyptian-born radical cleric Abu Hamza al-Masri.
Abu Hamza, who was the mosque's imam from 1997 to 2003, was later extradited to the United States, where he was convicted of supporting al Qaeda and Taliban terrorists, and sentenced to life in prison in 2015.
Among those known to have worshiped at the mosque during Abu-Hamza's time there are convicted shoe bomber Richard Reid and Zacarias Moussaoui, the so-called 20th hijacker of September 11.
The mosque has since undergone a series of high-profile reforms, including the installation of a new leadership board, led by the Muslim Association of Britain.
Resident Cynthia Vanzella said she was in bed when she heard people shouting. Vanzella said she went to the window and saw "loads of people gathering" in a corner across the road from her window.
"They were very nervous, shouting very loud, trying desperately to make some signs to a police car that was ... just passing the road," she told CNN.
"I saw so many of them crying, screaming, trying to get the police and the ambulance," she said.
She added: "I saw a lot of people injured. They were helping on the pavement and trying to help them to get away from the scene."
Vanzella said she saw police put a man into a police car and take him away, but she didn't see them arrest him.
"People were shouting this is an act of terrorism, even though he's white," another witness, Hillary Briffa, said, referring to the man taken away be police.
"These were the kinds of comments people were yelling out," she said.
She added: "Everybody was clamoring around and shouting at the man ... There was a lot of shouting in Arabic, so I can't tell you exactly what was being said."