London police say five people, including the attacker, were killed after a car ploughed into pedestrians and a man went on a stabbing spree, before being shot dead close to the British parliament buildings.
“Islamist-related terrorism is our assumption,” Rowley told journalists. He said police believe they know the identity of the attacker, but he declined to provide details.
The male assailant was shot dead after mowing down pedestrians and stabbing a policeman.
Rowley said the violence started when a car was driven over Westminster Bridge, hitting and injuring a number of civilians and three police officers on their way back from a commendation ceremony.
The car then crashed into a fence close to parliament, where at least one man, armed with a knife, continued the attack and tried to enter the building.
Many people were seen lying on the ground on Westminster Bridge – some bleeding heavily and apparently unconscious. Some of the wounds suffered by the victims were described as “catastrophic”. One woman with serious injuries was rescued from the River Thames by port authorities.
Witnesses initially reported multiple attacks near parliament.
“We saw a black vehicle [driving] at full speed and it ran down a number of people. I could see people flying all around,” tourist Babi Nagy told Al Jazeera. “Immediately it came to mind that this was a terrorist attack.”
Polish politician and journalist Radoslaw Sikorski posted a video on Twitter of the aftermath on the bridge, showing several injured people lying on the ground. Another witness reported seeing victims scattered along the street.
“As I was walking up the steps, there was a man who had fallen and medics were taking care of him. There was a lady who was also stabbed or shot. There was a lot of blood,” Martin Pearce, who was visibly shaken, told Al Jazeera at the scene .
Prime Minister Theresa May condemned the attack as “sick and depraved”.
“The location of this attack was no accident,” she said in a statement outside her Downing Street office late in the evening. “The terrorist chose to strike at the heart of our capital city, where people of all nationalities, religions and cultures come together to celebrate the values of liberty, democracy and freedom of speech.”
Security analyst Afzal Ashraf said extra vigilance by the public and authorities was now necessary. “One of the features of these forms of attacks is a follow-on attack. They like to have publicity; the potential threat is huge,” he said.
The last major attack in London was in July 2005, when a co-ordinated series of bomb blasts targeted its public transportation system during rush hour. The bombings killed 52 people and wounded more than 700 others.