Media playback is unsupported on your device Media caption Russian emergency officials reportedly described radiation levels on the burning nuclear submarine as being "normal"

A fire has broken out during repairs to a Russian nuclear submarine at a dock near the northern port of Murmansk.

The Russian Emergency Ministry said there had been no leak of radiation, and nobody was injured.

The Yekaterinburg submarine was being repaired when wooden structures in the dock caught fire and the flames spread to the vessel, say Russian media.

Eleven fire crews and a navy launch fought the blaze, which has now been put out.

Local media reports said a helicopter was also used.

'Fire cannot spread'

The Russian defence ministry said the nuclear reactors on the vessel were already shut down when the fire broke out.

All weapons had also been removed from the submarine before it entered the dock, the ministry said.

Image caption The Yekaterinburg is part of the Russian navy's Northern Fleet

As a huge plume of smoke billowed into the sky a Russian defence ministry spokesman, Igor Konashenkov, insisted there was no major risk from the fire.

"The power unit was switched off and is now safe," he told Russian state television.

"The fire cannot spread into the sub. There is no threat to onboard technical equipment."

Russian news agencies later said the submarine had been partially submerged in the dock to help extinguish the blaze.

The Yekaterinburg is a Delta-IV-class nuclear submarine. It was commissioned by the Soviet Union in 1985 and can carry 16 intercontinental ballistic missiles.

Safety on Russian navy submarines is a sensitive issue for the military following the Kursk disaster in August 2000.

The Kursk nuclear submarine sank in the Barents Sea off north-west Russia, killing all 118 seamen on board.

Investigators concluded that an explosion of fuel from one of its torpedoes caused the sinking.