A taxi driver who witnessed the aftermath of the incident in Edmonton, north London, told ITV News he saw police force their way into a house on Nightingale Road.
"They broke the door down and brought a man out," he said.
"There were dozens of police cars and a helicopter."
He added: "It's really worrying. It's very scary - we're always on the lookout."
More top news
From Kim Jong-Un's age to Pyongyang's new time zone - ten things you may not know about the secretive republic.
Five Palestinians were reportedly shot dead by Israeli soldiers after a fresh spate of clashes broke out in the conflict-ridden region.
This weekend: Patchy rain in the northwest, dry and bright elsewhere.