The UK's terror threat level has been raised from severe to critical.

29 people have been treated in hospital after a home-made bomb went off on a London Underground train this morning.

Police say most suffered 'flash burns' from the explosion at Parsons Green station.

As the bomber who attacked the train remains at large, British Prime Minister Theresa May says the UK's now on the highest level of terror alert.

Armed soldiers will be manning sensitive and high security locations around Britain over the weekend, in order to free up police.

The attack has been claimed by the Islamic State group.