According to a police report, the man is one of four suspected bombers sought by police after blasts on subway trains and a bus the previous day.
The as-yet unidentified man was held at an apartment in south London on Friday afternoon, near to Stockwell subway station where another suspect was shot dead by anti-terror police that morning.
He was being held under a section of Britain’s 2001 anti-terrorism law relating to the “commission, instigation or preparation of acts of terrorism”, a police spokeswoman said.
Residents in a block of flats in Lambeth, South London, near Stockwell station, said armed police stormed onto the estate that afternoon and a man was led away after one apartment was raided.
Police have launched a massive hunt for four men whose rucksack-borne bombs seemingly failed to explode properly on Friday as they targeted three subway trains and a bus, a virtual repeat of suicide attacks on July 7 in which 56 people died, including the attackers.
According to “senior security sources” sited by Saturday’s edition of The Sun newspaper, the arrested man is the bomber whose device exploded on a Number 26 bus in east London, injuring no-one but blowing out some windows.
“One down.. three to go,” was the headline on the paper’s front page, above a picture of the arrested man being driven away wearing a plastic suit to protect potential evidence on his clothes.
The picture was too grainy to tell whether the man looked similar to a security camera image of the bus bomber released earlier by police.
London police have issued photographs of four men wanted in connection with Thursday’s botched attempts to bomb the city’s transport network.
It is not yet clear if a man shot dead at the Stockwell London underground rail station on Friday was one of them.
The killing sparked panic on a crowded station platform and fuelled London’s sense of unease after the July 7 suicide attacks.
Witnesses at Stockwell spoke of panic as a man of south Asian appearance wearing an unseasonably thick jacket vaulted over station barriers as police chased, tackled, then shot him.
“I’ve never seen anything like it in my life. I saw them kill a man basically. I saw them shoot a man five times,” witness Mark Whitby told BBC television.
Police said the man was connected to their investigation but did not say how.
They removed his body from the station in the evening as the capital struggled to return to normal.
“It is not yet clear whether he is one of the four people we are seeking to identify and whose pictures have been released today,” they said in a statement.
The Abu Hafs al Masri Brigade, an al Qaeda-linked group, has claimed responsibility for both sets of bombings.
“Our attack in the heart of the infidel British capital is nothing but a message to all European governments that we will not rest until all the infidel troops leave Iraq,” the group said in a statement on an Islamist Web site.
The group’s claims of responsibility for previous attacks in Europe have been discredited by security experts.
Sheikh Omar Bakri Mohammed, one of Britain’s most outspoken Islamic clerics, said he believed militant Islamists would go on attacking until the government pulled its troops out of Iraq.
As forensics experts studied the trains and bus hit by Thursday’s small, near-simultaneous blasts, police were called to a series of security alerts in London, Birmingham and Leeds.
As the manhunt intensified, commuters eyed one another nervously on buses and trains.
“Passengers are more nervous as they get on the bus, they glance at people with bags and I am always looking at people’s bags,” said bus driver Danny Prescott.
A union official warned that hundreds of underground train drivers might refuse to work if there were more attacks.