WATCH: Police 'disguised as homeless tramps' storm London 'bucket bomb' suspect

British police posed as homeless tramps at a busy London bus stop when they rushed and arrested a suspect in connection to the Tube train bucket bombing.

Shouting “I’m sorry! I’m sorry”, Yahya Faroukh was handcuffed, wrapped in plastic to preserve evidence and pinned against a wall outside Aladdin's Fried Chicken.

The 21-year-old had worked at the fast food shop for the past nine months and is now being questioned by counter-terrorism officers following Friday's explosion at Parsons Green station that injured 30 people.

Shocked onlookers filmed the arrest as it unfolded on Saturday evening (local time).

"I heard from some other members of staff that one of the undercover cops was dressed as a homeless person when they jumped out at him," one worker inside the store told local media.

"It happened near the bus stop and supposedly the police officer was sitting on the ground then jumped out at him."

Yahya Faroukh was handcuffed outside the fast food store where he works. Source: Snapchat
The arrest comes after a bucket bomb on-board a London Underground train injured 30 people. Source: AP

Witnesses said police converged on the terrified Syrian native, who was heard repeatedly screaming, "I'm sorry, I'm sorry" as the contents of his bag scattered onto the footpath.

"The officers came out of nowhere, they had obviously had a tip off, they were acting like they were waiting for a bus, just standing there, they turned around and just took him to the floor," the witness recalled.

"Someone - a friend who was with him - tried to pick up his phone but the CID officers were shouting at him telling everyone not to touch anything.”

Witnesses said the 21 year old screamed that he was sorry as police pinned him against the wall.
A fences has been erected around the house where the man's foster carers live. Source: AAP

An 18-year-old man has also been brought in for questioning over the incident now being dubbed "bomb in a bucket".

Meanwhile police have erected a high, solid metal security wall around the Cavendish Road house of foster carers Ronald Jones, 88, and his wife Penelope, 71, plus several neighbouring properties, blocking off the street.

It is understood the longtime foster parents had been caring for Faroukh and the teenager in question.