(CNN) -- A vehicle hit pedestrians in London's Finsbury Park community, causing "a number of casualties being worked on at the scene," according to authorities.
London's Metropolitan Police said officers were called just after midnight Sunday to an incident on Seven Sisters Road. "There has been one person arrested. Inquiries continue. More information will be released when confirmed," police said.
London Ambulance tweeted: "We have sent a number of resources to an incident in Seven Sisters Road. More information will follow when we have it."
Transport for London tweeted that Seven Sisters Road was closed northbound at Hornsey Road and southbound at Rock Street.
CNN national terror analyst Peter Bergen said the neighborhood has a large Muslim population and the nearby mosque has 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."
The Muslim Council of Britain tweeted, "We have been informed that a van has run over worshipers as they left #FinsburyPark Mosque. Our prayers are with the victims."
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 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.
Islington's Seven Sisters Road, where the attack 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.
One witness, Rayan, said she was inside the mosque, where a lot of people were praying for Ramadan.
"First I thought it was just a fight or maybe someone was stabbed. But it was a terrorist attack," she told CNN.
"He targeted people and he killed people. He tried to kill a lot of people. So obviously, it was a terrorist attack. He targeted Muslims, this time," she said.
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 to 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."
Developing story. More to come.