"He just came into all of us".
The body said it was a "violent manifestation of Islamophbia" and called for extra security around mosques.
Prime Minister Theresa May described the attack as a "terrible incident" but said it is a "potential terrorist attack" and that she would "chair an emergency meeting" later Monday morning.
The council tweeted that its prayers were with the victims.
Worshippers left the mosque right after midnight when the van struck.
The Sky TV reported that "at least 10 people" were hit by the van. Separately, a suicide bombing killed 22 people in Manchester May 22 and another attack claimed five victims and injured dozens outside the British parliament in central London on March 22.
Some have already suggested they suspect the incident was terrorism, though again, authorities have not confirmed that.More news: Trump not included in Russia probe: lawyer
The neighborhood has two mosques, and several hundred worshipers would have been in the area after attending prayers as part of the Muslim holy month of Ramadan.
One person was in custody and the investigation was ongoing, police said.
She said her thoughts were with the injured, their loved ones and emergency officials who responded to the incident.
The Associated Press reports that Finsbury Park Mosque, one of four mosques in the Islington borough, had been associated with extremist ideology in the wake of the 9/11 attacks in the US.
Prime Minister Theresa May confirmed the crash is being investigated as a terrorist attack and said her thoughts were with those who had been hurt in "this bad incident". "It appears from eyewitness accounts that the perpetrator was motivated by Islamophobia".
The crash occurred outside the Finsbury Park Mosque in London.
Earlier this month, three men who pledged allegiance to the Islamic State terrorist organization, rammed a van into pedestrians on London Bridge before stabbing passers-by, killing eight.
Abdulraman Aidroos, who witnessed the incident, said "a white British man" shouted, "I am going to kill Muslims" before driving his auto into pedestrians.
Britain set its terror at "severe", meaning an attack is highly likely, after a pair of incidents recently.