A suspected terrorist carrying knives was arrested by heavily armed police close to the British Houses of Parliament and the Prime Minister’s home in central London.

And in ongoing counter-terrorism operations in London, a woman was shot by police as well as four other people arrested on Thursday.

The arrest of the 27-year-old British man at Parliament Square in Whitehall, near the scene of last month’s deadly terror attack on Westminster Bridge and Parliament, came during a stop-and-search in an ongoing security operation, police said.

The bearded man, described by a witness as acting “very calm”, was carrying a rucksack containing at least three knives when he was detained shortly before 2.30pm Thursday local time.

“Knives have been recovered from him. He is being detained under the Terrorism Act and is in custody in a south London police station,” police said.

Pictures of the man’s arrest on social media showed a large group of officers surrounding the suspect, while witnesses saw police officers standing next to knives lying on the ground.

It is understood the arrest of the 27-year-old suspect was “intelligence-led” and was made as part of a joint operation being carried out by MI5. 

The circumstances of the swoop would suggest the suspect may have been under some form of surveillance prior to his arrest, with The Independent newspaper reporting that police had followed him before the arrest as he travelled on the London Underground.

The investigation had been handed to its Counter Terrorism Command and that there was “no immediate known threat” to the public.

Police said no one was injured in the incident.

Prime Minister Theresa May was not at her No.10 Downing Street home at the time of the arrest because she was campaigning in northern England ahead of the June 8 election.

“The man … was arrested on suspicion of possession of an offensive weapon and on suspicion of the commission, preparation and instigation of acts of terrorism. Knives have been recovered from him,” police said.

A security source told Reuters the London resident was known to counter-terrorism officers and the domestic intelligence agency MI5 before his arrest.

Streets in the vicinity of the arrest were closed for two hours. Police also closed the main gates to Parliament, a witness said.

“I am aware that an individual has been arrested in Whitehall today and that that individual has been arrested on the basis of a terrorism charge,” Ms May told Sky News.

“Obviously I can’t say much more about it because it is an ongoing police investigation but I think it shows that our police, and our intelligence and security services, are on the alert as they always are looking to keep us safe and secure.”

Police said the suspect was being questioned at a south London police station.

Terrorist Khalid Masood launched an attack in March which killed five, including Police Constable Keith Palmer, very close to the location of today’s arrest.

UK swoops in counter-terrorism operation

The woman, shot by police, aged in her 20s was injured during the swoop at an address in Harlesden Road, in north-west London, shortly before 7pm on Thursday (local time).

The operation was not connected to the earlier incident near Westminster, Scotland Yard said.

A Met Police statement said a 20-year-old man was arrested near the address and a 16-year-old boy and 20-year-old woman were detained inside the property.

A woman, aged 43, was arrested in Kent a short while later.

All four are being held on suspicion of the commission, preparation and instigation of terrorist acts and are in custody at a south London police station.

All four are being held at a south London police station on suspicion of the commission, preparation and instigation of terrorist acts.

– with agencies