The incidents were an echo of the July 7 attacks, however only one person was injured and there were no deaths after the bombs, carried in rucksacks, seemed to fail to properly detonate.
Three of the devices are reportedly the same size and weight as the July 7 bombs with the same chemicals used.
Thursday’s attacks took place around 12.30 local time, with bombs at Shepherd’s Bush station in London’s west, the central Warren Street station, Oval in the south and on a bus in east London’s Shoreditch.
The would-be bombers managed to flee, and police are now combing CCTV footage for clues, as well as undertaking a massive forensic examination, however have refused to elaborate on their investigation.
Met Police Commissioner Sir Ian Blair told a press conference that it is too early to tell whether Thursday’s attacks are linked to events two weeks ago.
He said the fact that the bombs remain unexploded at the scenes is very helpful.
“Clearly the intention must have been to kill. You don’t do this with any other intention,” he said.
Witnesses have told of hearing loud pops, like guns or corks, with smoke pouring from the rucksacks, leading police to believe just the detonators exploded.
One London businessman told the Daily Mail newspaper that after the bang, he came face-to-face with a dazed man lying on the floor on top of his smoking rucksack on a train near Shepherd’s Bush station.
Abisha Moyo said he was on a subway train near Shepherd’s Bush station in west London, the site of the first reported near-simultaneous train blasts, when he was startled by a loud bang.
He described the smartly-dressed young man as appearing shocked and dazed.
“He had his eyes shut and there was a puff of smoke coming from the bag,” Mr Moyo said, adding that he asked the man if he was all right before realising it was a bombing attempt and fled from the train.
Ivan McCracken, on the train at Warren Street, said fellow passengers described seeing a man carrying a rucksack which exploded.
“It was a minor explosion but enough to blow open the rucksack. The man then made an exclamation as if something had gone wrong. At that point everyone rushed from the carriage.”
According to newspaper reports, police have recovered all four rucksack bombs, which may provide clues on those who helped the four British Muslim suicide bombers who died in the July 7 attacks.