A man has been arrested on suspicion of murder and attempted murder after a van was driven into pedestrians near Finsbury Park Mosque early yesterday.
Police Scotland said it would have an increased presence at the country’s 84 mosques to provide reassurance to local communities.
One man died in London following the attack on those leaving evening prayers after breaking the Ramadan fast.
Witnesses described hearing the man, who was detained by members of the public at the scene, shout: “I’m going to kill Muslims.”
The man arrested on suspicion of carrying out the attack is understood to be 47-year-old Darren Osborne from Cardiff.
Police last night confirmed searches were being carried out at a residential address in the Welsh capital.
Deputy Assistant Commissioner Neil Basu, of the Metropolitan Police, said: “Our thoughts are with all those affected by the incident at Seven Sisters Road and their families, friends and communities.
“This is being treated as a terrorist incident and is being investigated by the counter terrorism command.
“The investigation is ongoing and we are working fast to know the full details of how and why this took place.
“All the victims were from the Muslim community and we will be deploying extra police patrols to reassure the public, especially those observing Ramadan.”
Earlier in the day, security minister Ben Wallace confirmed the attacker was not known to the intelligence services.
He said: “What I can say on this case is this individual, so far as we know at the moment, was not known to us, but we are aware of a rise in the far right.”
The attacker, who is believed to have acted alone, struck as the area was busy with worshippers attending Ramadan night prayers at the mosque.
Prime Minister Theresa May condemned the incident as “every bit as sickening” as the recent atrocities in London and Manchester.
After meeting faith leaders at Finsbury Park Mosque, she said: “The terrible terrorist attack which took place last night was an evil borne out of hatred and it has devastated a community.
“I am pleased to have been here today to see the strength of that community coming together, all faiths united in one desire to see extremism and hatred of all sorts driven out of our society.
“There is no place for this hatred in our country today and we need to work together as one society, one community, to drive it out, this evil which is affecting so many families.”
Police and community leaders have praised those who restrained the van driver and stopped others from attacking him before police arrived.
Imam Mohammed Mahmoud was hailed for his efforts to calm the chaotic situation in the aftermath of the attack and was said to have used his body to shield the suspected terrorist from the fury of onlookers.
Witnesses said the suspect was smiling and waving as he brought carnage to Seven Sisters Road, with video posted online showing him give a nonchalant wave as police put him in the back of their vehicle.
Other footage showed a scene of chaos as people could be heard shouting and screaming amid the chaos, with bloodstains visible on the pavement.
One witness described being surrounded by bodies in the wake of the incident outside the nearby Muslim Welfare House.
Another witness, who wanted to be identified as Abdulrahman, which is not his real name, said: “I managed to get the driver of the van.
“He wanted to run away and was saying ‘I want to kill Muslims.’
“So he came back to the main road and I managed to get him to the ground and me and some other guys managed to hold him until the police arrived.”
Abdulrahman claimed the driver said “Kill me”, as he was being held on the ground.
He is also alleged to have told the injured: “You deserve it.”
Officers were in the immediate vicinity as the attack unfolded and responded within one minute.
Police declared it a terrorist incident within eight minutes.
After chairing a meeting of the Government’s Cobra emergencies committee earlier, Mrs May said the attack was “every bit as insidious and destructive to our values and our way of life” as the recent string of terror attacks apparently motivated by Islamist extremism.
“We will stop at nothing to defeat it,” she added.
Eight people were taken to hospital, with one since discharged, while two others were treated at the scene.
All of the casualties were Muslims.
Police said it was too early to say if the man who died did so directly because of the attack, as he was already receiving first aid from the public at the scene when it happened.
Images of the van used in the attack showed it was rented from Pontyclun Van Hire in Pontyclun, near Cardiff.
South Wales Police are working with officers from London on the investigation.
Communities and Local Government Secretary Sajid Javid also visited the scene and said he will seek advice from the local community as to what measures the authorities can take to give Muslims across the country “maximum reassurance” that they are being protected.
“The perpetrator of this attack - and those terrible attacks that we saw recently in Manchester and London - their intention is to seek to divide society. My message to them is that they will always, always fail,” he said.
Flowers have been laid near the scene, with one card reading: “This is an attack on all Londoners - and on my community.”
In a statement, the Muslim Council of Scotland condemned the attack in the “strongest possible terms”.
It said: “This attack was aimed directly at the vibrant Muslim community during the month of Ramadan at a time when many families would have been returning home after night time prayers.
“Our thoughts and prayers are with the victims, the injured and anyone affected by this tragedy. Our heart goes out to the people of London who have been through so much in the last few months and are still waiting for news on many friends and family in the Grenfell Tower tragedy.
“This attack goes to show how hate and terrorism has no religion or face. The motive of these people is to spread division. Together, as a united community, we can defeat those who seek to divide us.”
Assistant Chief Constable Nelson Telfer, of Police Scotland, said: “There is no specific threat to Scotland, however, Police Scotland is increasing armed patrols in response to the attack in London.
“We continue to engage with all communities providing reassurance and appropriate support.
“Communities absolutely do defeat terrorism: if you see or hear something that could be terrorist related, act on your instincts and call the police on 101 or, in emergency 999, or in confidence on 0800 789 321.”