Mark Rowley, acting deputy commissioner at the Metropolitan police, on Thursday revised down the number of victims from Wednesday’s rampage

to three from four.

Rowley said police had searched addresses in London, Birmingham, and other parts of the country in their investigation into the attack

, in which a man ploughed into pedestrians in a car and then went on a stabbing spree before being shot dead.

“It is still our belief that the attacker acted alone was inspired by international terrorism,” Rowley said.

Some 40 people were wounded in the attack, 29 of whom were being treated in hospital, he added. Seven were still in critical condition.

Rowley said there was a mix of nationalities among the dead but gave no details. The victims were a police officer who was stabbed and two members of the public; a woman in her mid-40s and a man in his mid-50s.

The fourth dead was the attacker.

Al Jazeera’s Barnaby Phillips, reporting from London, said: “The absolute priority of the police at this point in time would be to know what sort of accomplices, if any, the assailant had. What sort of assistance, if any, did the assailant have and whether he belonged to any sort of network.”

Rowley said he had no specific information about any further risk to the public, but repeated that more officers were on the streets – armed and unarmed – and that many had leave cancelled or were working extended hours.

REPORTER’s NOTEBOOK: Seeking solace in wake of the Westminster attack

UK Prime Minister Theresa May condemned the attack

on Westminster Bridge and at the iconic parliament building in the shadow of Big Ben as “sick and depraved”.

“The location of this attack was no accident,” she said in a statement outside her Downing Street office late on Wednesday 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.”

Some of the wounds suffered by the victims were described as “catastrophic”. One woman was pulled out alive from the River Thames with serious injuries by port authorities.

“We saw a black vehicle 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 this was a terrorist attack.”

Polish politician and journalist Radoslaw Sikorski posted a video on Twitter of the aftermath on the bridge, showing several wounded people lying on the ground.

Another witness said he saw 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 told Al Jazeera

at the scene .

The last major attack to hit London was in July 2005, when a coordinated series of bomb blasts targeted its public transportation system during rush hour. The bombings killed 52 people and wounded more than 700 others.

Mayor Sadiq Khan said Londoners will “never be cowed by terrorism”.

“There will be additional armed and unarmed police officers on our streets from tonight in order to keep Londoners, and all those visiting our city, safe,” he said.

“I want to reassure all Londoners, and all our visitors, not to be alarmed.”

Leaders across the world condemned the attack, while lights on the Eiffel Tower in Paris were switched off at midnight in solidarity with victims of the attack.

US President Donald Trump and French President Francois Hollande both spoke to May and Chancellor Angela Merkel said Germany stood with Britons “against all forms of terrorism”.

“Spoke to UK Prime Minister Theresa May today to offer condolences on the terrorist attack in London,” Trump tweeted.

Turkish President Recep Tayyip Erdogan said that “Turkey feels and shares deeply in the United Kingdom’s pain” and that it stood in “solidarity” with Britain “in the fight against terrorism”.

Several international tourists visiting one of London’s most iconic sights were caught up in the violence.

Five South Korean tourists were wounded, Seoul’s foreign ministry said, while the Romanian government said two of its citizens were also injured. DM