Police have declared a "major incident" after a van ploughed into a group of pedestrians in north London.
Early reports suggest the victims were worshippers leaving night prayer during Ramadan, with witnesses telling HuffPost UK ten people were hit by the vehicle.
The Metropolitan Police said the incident left "a number of casualties" after it was called to Seven Sisters Road, Finsbury Park, north London, at around 12.20 on Monday.
Reports suggest the incident happened outside the Muslim Welfare House rather than the mosque in the area.
One person has been arrested and a HuffPost UK reporter witnessed police detaining a second person several hours after the collision. Authorities declined to comment on the reason for the arrest.
London Ambulance Service said it had sent a number of ambulance crews and specialists teams had been sent to the scene.
A Met Police spokesman said: "Officers are on scene with other emergency services. There are a number of casualties being worked on at the scene. There has been one person arrested. Enquiries continue."
HuffPost UK's Paco Anselmi is in Finsbury Park, and witnessed increasingly angry scenes.
One local resident told HuffPost UK: "One thing that is clear. This happened after night prayer that us Muslims pray during Ramadan. It was clearly an act that was planned and an act that was done with full intention."
Others were irritated what appeared to be a deliberate attack was not being treated as terror.
"If it was somebody with a beard wearing a different type of clothes, you would be calling it terrorism," one local man told the BBC's Nick Robinson. "Our concern is you are the press you should speak the truth."
Another man said witnesses said they saw three people in the vehicle.
Cynthia Vanzella, a woman who lives near the scene, told CNN she heard the collision from her home and went to a window to see people "desperately trying to make some signs to a police car."
"I saw a lot of people injured," she said. "They were helping on the pavement and trying to help them to get to the scene."
The chairman of the mosque, Mohammed Kozbar, described the incident as a "cowardly attack" and said there were many injuries.
Britain's terrorist alert has been set at "severe" meaning an attack is highly likely.
Earlier this month, a van veered into pedestrians on London Bridge, setting off vehicle and knife attacks that killed eight people and wounded many others on the bridge and in the nearby Borough Market area.
Three Muslim extremists who carried out the attack were killed by police.
Prime Minister Theresa May has described the attack on worshippers near Finsbury Park mosque as a "terrible incident", adding: "All my thoughts are with those who have been injured, their loved ones and the emergency services on the scene."
Labour leader Jeremy Corbyn said his "thoughts are with the community affected by this awful event".