LONDON (AP) - Armed police carrying out a counterterrorism operation Thursday swooped in on a man they said was carrying knives in a bag near Britain's Parliament and arrested him on suspicion of planning terrorist acts.
A European security official familiar with the individual said the suspect was known to British security agencies and was thought to have been inspired by the Islamic State group.
The official, who spoke on condition of anonymity to discuss sensitive intelligence matters, said the discovery of knives suggested an attack might have been close to fruition. Authorities haven't released the man's name.
London's Metropolitan Police said the 27-year-old suspect was stopped and detained "as part of an ongoing operation" by the force's counterterrorism unit.
No one was injured in the incident, which unfolded just yards from where an attacker killed five people with a vehicle and a knife last month. It sent a jittery jolt through an area that has been on edge since the March 22 attack.
Police said knives were recovered during the operation and there was "no immediate known threat" to the public.
Police said the man was being held at a London police station on suspicion of possession of an offensive weapon and on suspicion of the commission, preparation and instigation of acts of terrorism.
As armed police blocked off Whitehall, a street lined with government buildings that is the main artery of London's government district, witnesses reported seeing and a man on the ground surrounded by police.
Ian Moss, who was traveling on a bus on Whitehall, said the man didn't appear to be struggling.
"He had police pointing arms at him though," Moss said.
A bearded, black-clad man could later be seen standing on the sidewalk, surrounded by police, before being put into a police vehicle.
"He was standing with his back toward the public and his face against the wall," said witness Chris Kacyk, who arrived in the area just as the suspect was taken into custody. "The guys made sure he could not move. He was tightly cornered by three heavily armed police officers with machine guns and two undercover detectives."
Kacyk said he saw several knives - including one very large one - on the ground next to the suspect's knapsack.
After the arrest, forensic officers pored over the scene. A black bag and at least three knives could be seen on the ground.
The man was arrested yards from the gates to Downing Street, where the prime minister's residence is located. Prime Minister Theresa May, who is campaigning in a national election, was not there at the time.
May said 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."
Thursday was Parliament's last sitting day before Britain's June 8 election.
Police believe Masood, 52, a British-born Muslim convert with convictions for violence, acted alone.
Police said there has been a surge in knife crimes in London in the past year.
Britain's official threat level from international terrorism stand at the second-highest level, "severe," meaning an attack is highly likely.