"A man has been arrested in Whitehall this afternoon, at approximately 14:22 (1622 UTC), following a stop and search as part of an ongoing operation," London Metropolitan Police said in a statement on Thursday afternoon.

The police added that the man in his late 20s had been detained under the Terror Act 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."

They added that there was no immediate known threat to the public and that the counter-terrorism unit would continue to investigate the incident. No one was injured, police confirmed.

Read more: Are Europeans getting used to terror attacks?

Witnesses reported seeing armed police blocking off the area near Parliament Square and the Palace of Westminster and encircling a man dressed in black who was lying on the ground.

Media photos also showed forensic teams examining what appeared to be two knives on the pavement. However, police did not specify the number of knives recovered.

An arrest in the political heart of London

The arrest took place in the United Kingdom's political nucleus, a stone's throw away from the Houses of Parliament, where representatives were sitting for the last time before Britain's elections on June 8. Various government offices, as well as Prime Minister Theresa May's official residence in Downing Street, are also nearby.

A spokeswoman for Max confirmed the prime minister was not in London at the time of the arrest but had been informed of the incident.

The Prime Minister later praised British intelligence and security officials on Sky news. The arrest "shows that our police and our intelligence and security are on the alert, as they always are, looking to keep us safe and secure. I think we owe a huge debt of gratitude to these people," May said.

 

Security in the Whitehall area had been increased in the aftermath of the March 22 terror attack, in which a sole attacker rammed a car into pedestrians on Westminster Bridge, killing four, and then proceeded to stab a police officer to death inside Parliament's gates. The British-born attacker, Khalid Masood, was subsequently shot dead by police. He is believed to have acted alone.

cmb/sms (AP, Reuters, AFP)