Prime Minister Theresa May says the terror attack near a north London mosque is “every bit as sickening” as other recent ones to hit the UK.

She was speaking after a man died and 10 people were injured when a man drove a van into worshippers outside the Muslim Welfare House.

Eight people were taken to hospital after the attack outside the mosque, which is also a community centre.

A 48-year-old man has been arrested on suspicion of attempted murder. A group of people were helping a man who had collapsed when they were hit by the van just after midnight. The man has died, but it is unclear whether this was as a result of the attack.

This is the fourth terror attack in the UK in four months, after incidents in Westminster, Manchester and on London Bridge. Police said all the victims of the attack, which was in the area of Finsbury Park Mosque, were Muslim.

Many are believed to have just left evening prayers at the Muslim Welfare House after breaking the Ramadan fast.

Mrs May was speaking after chairing a meeting of the government’s emergency Cobra committee. She said the driver of the van acted alone, and police declared it a terrorist incident within eight minutes. The PM added that “there has been far too much tolerance of extremism over many years”. “It is a reminder that terrorism, extremism and hatred take many forms; and our determination to tackle them must be the same whoever is responsible.”

Metropolitan Police’s deputy assistant commissioner Neil Basu said the terror attack began when the van was driven into a man who was already being given first aid by the public on the pavement. Several of those in hospital are “seriously injured”, he added.

“When the guy came out from his van he wanted to escape, run away, and he was saying ‘I want to kill Muslims. ‘I want to kill Muslims.’ “I hit him on his stomach… and then me and the other guys… we held him to the ground until he couldn’t move. We stopped him until the police came.”

Earlier, police also said the arrested man would be the “subject of a mental health assessment in due course”.

Extra police are being deployed to reassure communities, especially those observing Ramadan, Mayor of London Sadiq Khan said. “While this appears to be an attack on a particular community, like the terrible attacks in Manchester, Westminster and London Bridge it is also an assault on all our shared values of tolerance, freedom and respect,” he added.

This not the first time that Muslims – and specifically visible Muslim targets, namely mosques – had been targeted in an act of terrorism in the UK.

The threat from extreme right-wing groups has been growing in recent years, he said, noting that 16% of all terror arrests in the year to March were classed as “domestic extremism”.

Locals say this is a proudly multicultural area, where the biggest rivalry is whether you support Arsenal or their north London rivals, Tottenham.

Now the mood here is one of shock, as residents stand by the police cordon seeing the aftermath of yet another attack in London.

Mother-of-four Nicola Senior, 43, is walking back from taking her children to school when she stops to take in the scene. She said: “I’m frightened. Is there going to be retaliation? “I am fearful for my kids. Can we go to the park? Can we go to the church? It feels like this is happening all the time.”

An eyewitness told how he jumped out of the way of the van as it struck: “He just came into all of us. There was a lot of people. We got told to move straight away. “I was shocked, shocked, shocked. There were bodies around me.”

Another witness, who gave his name as Abdul, said the arrested man was shouting “kill me, I’ve done my job”.

Adil Rana, 24, said the suspected attacker was pinned to the floor by members of the public “and people were punching him and beating him, which was reasonable because of what he’s done”. “And then the imam of the mosque actually came out and said: ‘Don’t hit him, hand him over to the police, pin him down’.”

Forensics officers are examining a white van which has Pontyclun Van Hire on it – a firm from Rhondda Cynon Taff in south Wales. The firm said in a statement that it was “shocked and saddened” and co-operating with the police.

This incident risks playing right into the hands of those planning further attacks on vulnerable citizens in the UK.

Online followers of the so-called Islamic State have been quick to seize on the Finsbury Park attack as proof of what they see as widespread hostility towards Muslims who live in the West. Inevitably, it will be used by recruiters and propagandists to incite further attacks – extremism breeds extremism. The one thing that far right anti-Muslim extremists and violent jihadists have in common is the belief that peaceful coexistence between Muslim and non-Muslim is impossible.

The unified prayers and solidarity across communities that followed recent terror attacks are anathema to them. Extremists of both types want instead to divide society and will keep trying to bring this about by criminal acts of provocation such as this.

The Muslim Council of Britain said this was the “most violent manifestation to date” of recent Islamophobic incidents. “We expect the authorities to increase security outside mosques as a matter of urgency.”

Mohammed Kozbar, general secretary of Finsbury Park Mosque, gave a statement on behalf of a joint faiths group. He said that “an attack on one faith is an attack on all faith and communities”.

The group has appealed for calm, adding that “all of our efforts should be towards getting justice for the victims and ensuring our community stays the diverse, tolerant and welcome place we know it to be”.

Home Secretary Amber Rudd described it as an appalling incident, and said new funding for security at religious sites had recently been arranged. “We have a places of worship fund which we announced last summer, which is there to protect places of worship like mosques. We will make sure that we do all we can to reduce these sort of attacks.”

Labour’s shadow home secretary and Hackney North and Stoke Newington MP Diane Abbott said on Twitter that police “must urgently review security for all mosques”.

Labour leader and Islington North MP Jeremy Corbyn has also visited the area. He said that “an attack on a mosque, an attack on a synagogue, an attack on a church is actually an attack on all of us”. “We have to protect each other’s faith, each other’s way of life, and that’s what makes us a strong society and community.”

Mr Corbyn will be attending prayers at Finsbury Park Mosque later on Monday with Islington Council Leader Richard Watts. Communities Secretary Sajid Javid has also been to the area, where he met residents and community leaders. He said it was a “despicable attack” which was intended to divide society, but added: “That will fail. These perpetrators will never succeed.”

Mr Javid also said he wanted to reassure Muslims around the UK that the government would “always take a zero tolerance approach to hate crime”.