LONDON - A teenager who had been convicted of planting a bomb on a London tube train last year was sentenced to life-long imprisonment on Friday.

The device planted by Ahmed Hassan, 18, described by a judge as "dangerous and devious," partially exploded during London's rush hour in September last year, injuring 51 people.

Hassan, an Iraqi asylum seeker in Britain who was found guilty of attempted murder, was ordered to serve a minimum of 34 years.

The judge said Hassan planned his attack with "ruthless determination and almost military efficiency while pretending to be a model asylum seeker."

British media said the trial heard Hassan blamed Britain for the death of his father in Iraq.

Prosecutors at the sentencing hearing said there would have been serious harm if the bomb which was packed with screwdrivers, knives, nuts and bolts had fully detonated.