Home Secretary Amber Rudd has said police are treating the attack on a North London mosque as a "terrorist incident".
Her confirmation comes hours after a man ploughed a van into a Muslim congregation leaving late night prayers on Seven Sisters Road.
One person has died and eight people were injured and they were taken to three hospitals around the city.
"My thoughts are with all those affected by the appalling incident at Finsbury Park," said Ms Rudd.
"I am in contact with the Metropolitan Police who have confirmed it is being investigated by their Counter Terrorism Command.
"We must all continue to stand together, resolute, against all those who try to divide us and spread hate and fear."
London Mayor Sadiq Khan denounced the mosque attack as "an assault on all our shared values of tolerance, freedom and respect".
Labour's shadow home secretary Diane Abbott called for police to review security at mosques. Her constituency in north London is not far from Seven Sisters Road.
Her call for more security around mosques was echoed by Fiyaz Mughal, the founder of an anti-Muslim incident watchdog, and who had been at the mosque on Friday, advising leaders to tell their congregations on the safest way to enter and leave the building.
Green Party co-leader Caroline Lucas said her thoughts were with the community and emergency services, adding: "We will not be divided."