London police are investigating what they're calling a "major incident in Seven Sisters Road".
Worshippers coming out of the Finsbury Road Mosque in London say that a van drove into the crowd.
At this point, it's unclear whether the van veered off the road accidentally or deliberately.
Several people are injured, according to British news reports, and one man has been arrested.
Update: British media outlets have reported that one man died and 10 others were injured.
Update: British media outlets have reported that a crowd wrestled the driver to the ground and held him until he was arrested. He's a 48-year-old white man who reportedly shouted that he wanted to kill all Muslims. People in the crowd said two other men in the van fled.
Update: British prime minister Teresa May was heckled when she visited the Finsbury Road mosque. Labout Party Leader Jeremy Corbyn. The mayor of London, Sadiq Khan, has described the event as a "horrible terrorist attack".