London's Metropolitan Police commissioner announced that the Muslim community attending prayers will see police protection in the wake of a man driving a van into a crowd of people outside a mosque in what authorities called a "terrorist attack."
One person who had been receiving first aid prior to the attack that occurred just after midnight prayers Monday died on the scene, but it is unclear at this time whether or not his death was a result of the attack. At least 10 people were injured.
A 48-year-old man was arrested at the scene on suspicion of attempted murder. No other suspects have been identified, police said.
Metropolitan Police Commissioner Cressida Dick said the incident, near Finsbury Park in the north of London, was "quite clearly an attack on Muslims."
She later told reporters Monday. "The people in the Muslim community attending prayers will see their police protecting them in the coming days and nights."
Prime Minister Theresa May called the incident, which mirrored other high-profile terror attacks in which vehicles were used as weapons, "every bit as sickening as those that have come before."
London Mayor Sadiq Khan said "terrorism is terrorism."
"It doesn't matter whether you're inspired by a perverse force of Islam -- a perverse version of Islam -- or by you're inspired by some other motives to try and terrorize others. The intention is the same, to divide communities, to make us stop leading the lives that we do," he said.
Khan said there has been a spike in hate crime, including against Muslims, since the recent London bridge attack.
Eyewitnesses interviewed by ABC News said people had gathered outside the mosque after prayers when the van drove into them.
A man identified as Jermain Jackman told the BBC the sidewalks were "packed with people walking home" when the incident occurred.
"It was a van that mounted the pavement as men and women were leaving the mosque to go home to their families and friends and their loved ones," Jackson said.
The Muslim Council of Britain called the incident a "terror attack" and the "most violent manifestation" of Islamophobia.
"During the night, ordinary British citizens were set upon while they were going about their lives, completing their night worship," the Muslim Council said in a statement, adding that "Muslims have endured many incidents of Islamophobia" over the past weeks and months.
"We urge calm as the investigation establishes the full facts, and in these last days of Ramadan, pray for those affected and for justice," the statement concluded.
Shortly after the incident took place, London Mayor Khan referred to it as a "horrific terrorist attack."
Khan also called it "a deliberate attack on innocent Londoners, many of whom were finishing prayers during the holy month of Ramadan.
"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," Khan said in a statement.
A mosque with a complicated history
Monday's violence was targeted at Muslims who were outside of the Muslim Welfare House, near the Finsbury Mosque.
The Finsbury Mosque, which opened in 1988, is the site of where Abu Hamza, an Egyptian cleric and a believer in Islamic fundamentalism and militant Islamism, once preached.
Hamza was convicted in US Federal Court in Manhattan and sentenced to two consecutive life sentences for terrorism related charges in 2015.
A violent year for the U.K.
The attack at Finsbury Park represents the fourth such terrorist attack to strike the U.K. in 2017.
Earlier this month, a van rammed pedestrians on London Bridge, setting off vehicle and knife attacks that left eight people dead and many other injured on the bridge and in the nearby Borough Market area. Three Muslim extremists who carried out the attack were killed by police.
There was also an attack at an Ariana Grande concert in Manchester, where a bomber set off an explosion that killed more than 20 people, and three people were killed, including a police officer, and at least 29 people were hospitalized following an attack at Westminster Bridge in March.
Alexander Meleagrou-Hitchens, the research director of the Program on Extremism at George Washington University, told ABC News following the attack on London Bridge that defending against terror attacks in modern era was particularly challenging.
"Stopping everyone who rents a van or buys a long-knife is really difficult," Meleagrou-Hitchens told ABC News. "Once that person is on the road, it's just very hard to stop them."
ABC News' Joshua Hoyos, Rex Sakamoto and The Associated Press contributed to this report.