LONDON: Scotland Yard today scrambled to identify the attackers who tried to blow up a packed Tube train in London, as the UK's terror threat level was raised to the highest.
An improvised explosive device (IED) exploded at Parsons Green station yesterday, injuring 29 people.
The Islamic State militant group claimed the responsibility for the attack.
Metropolitan Police Assistant Commissioner Mark Rowley said police were "chasing down suspects".
Detectives used CCTV images from the station and train to single out the suspect believed to have planted the homemade device, but were still working to identify the bomber.
Raising the terror status to its highest level, which means another attack is considered imminent, Prime Minister Theresa May said military personnel would replace armed police "on guard duties at certain protected sites which are not accessible to the public".
"The public will see more armed police on the transport network and on our streets, providing extra protection. This is a proportionate and sensible step which will provide extra reassurance and protection while the investigation progresses," she said.
Investigators fear the bomb had the potential to cause huge devastation if fully detonated.
It is the fourth time the terror threat level has been raised to critical in the last 11 years - most recently after the Manchester Arena bombing.
Counter-terror police are being assisted by MI5 in their hunt for the bomber.
It is the fourth time the terror threat level has been raised to critical in the last 11 years - most recently after the Manchester Arena bombing.
The Mayor of London, Sadiq Khan, said: "The national threat level has now been raised to critical after the evil and cowardly terrorist attack at Parsons Green.
"As the Prime Minister has said, this is our highest level of security preparedness.
"I utterly condemn the hideous individuals who target innocent people and attempt to use terror to harm us and destroy our way of life," he said.
Yesterday 's attack was the fifth terrorism incident in the UK this year. But it's the only one in 2017 in which nobody has died. The previous four saw 36 people killed.
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