UK terror threat level raised to 'critical' after London Tube explosion

The terror threat level in the United Kingdom has been increased from 'severe' to 'critical', after an explosion which injured 29 people on a crowded London Underground train.

The terror threat level of 'critical' means that another attack is about to happen.

The police have called it as a terrorist incident and are looking for suspects.

Prime Minister Theresa May, called the blast a “cowardly attack” and said that the public will see more armed police on the transport network and on the city's streets to provide extra protection.

The Prime Minister also said that people should carry on with their daily lives, but have a careful watch for possible danger or difficulties.

No arrests have been made so far while terrorist group ISIS has claimed involvement in the explosion through its news agency that a "detachment" from the group had carried out the attack. However, ISIS provided no proof to back up its involvement.

The blast happened during the morning rush hour at about 8:20 AM local time on Friday at Parsons Green Tube station, a leafy stop on a busy commuter line from southwest London into the center of the British capital.