The driver has been arrested on suspicion of attempted murder.
Police said all of the victims were members of the Muslim community. He said: "The attack unfolded whilst a man was receiving first aid from the public at the scene; sadly, he has died".
Asked if the suspected terrorist attack was being treated as seriously as others, he told BBC News on Monday: "I'm treating it absolutely as seriously as any other attack".
"My message to the Government is, the plans you have to change the police funding formula so London loses more money: don't do it".
Earlier this month, three men drove into pedestrians on London Bridge before getting out of their van and attacking people in nearby Borough Market, leaving eight dead and at least 48 injured.
Counter-terrorism coordinator Neil Basu said the attack had "all the hallmarks of a terrorism incident".
"Due to the nature of this incident extra policing resources have been deployed in order to reassure communities, especially those observing Ramadan", the Guardian quoted the statement as saying. "I don't think people understand how much these attacks affect all of us". "I'm exhausted and I want my son to be safe".
London police closed the area to normal traffic.
He said: "Our heartfelt sympathy, thoughts and prayers are with the victims".
"I've heard stories form the imam who stopped local residents from understandably taking out their anger on this terrorist", Khan said at a press conference.
The Finsbury Park mosque was associated with extremist ideology for several years after the 9/11 attacks in the United States, but was shut down and reorganized.
Picture taken with permission from the Twitter feed of Thomas Van Hulle @Thomasvanhulle showing police activity on the Seven Sisters Road in north London, where one person has been arrested after a vehicle struck pedestrians, leaving "a number of casualties".
BuzzFeed's James Ball was told by a witness, Abdulrahman Aloudi, that the attacker yelled "kill me, kill me, I want to kill all Muslims".
Some people at the scene also complained that police took too long to arrive.
22 May: Suicide bomber Salman Abedi, a 22-year-old British man of Libyan origin, blows himself up outside a pop concert in Manchester.