A bombing in London has injured at least 20 people. Police say that the attackers detonated a bucket bomb during the morning rush hour at London's Parsons Green Subway station.

A 2nd bomb was located at the scene and police are actively disarming it.

Police are treating the blast as a terrorist incident after commuters reported a "fireball flying down a carriage" as the bomb, hidden in a bucket in a Lidl bag, partially detonated inside the carriage.

This appears to be the fifth major terror attack on British soil in six months.