A Russian nuclear submarine
A Russian nuclear submarine caught fire, blazing for several hours. Reuters

The Orel submarine which is capable of carrying nuclear-tipped cruise and anti-submarine missiles caught fire while under repair in a dry dock.

"The rubber insulation between the submarine's light and pressure hull is on fire," Tass reported.

The blaze broke out while the ship was under repair in the Zvezdochka shipyard in Severodvinsk, about 1,000 kilometres (620 miles) north of Moscow on the White Sea. After attempting to put out the flames for several hours, officials finally let water into the dry dock to extinguish the fire completely.

However, a spokesman for the shipyard told Interfax news agency that it could take another two hours to stop the burning.

"The fire has been contained, they continue to fill the dry dock with water," he said.

Officials stated there was no danger of explosion or radiation leak and that all of its weapons and reactor fuel had been removed before the repairs were carried out, according to an AP report.

Ilya Zhitomirsky, a spokesman for the United Shipbuilding Corporation which runs the shipyard, said no one was injured in the fire, which he said started in the vessel's insulation.

"There is no threat of environmental or radioactive contamination as the result of the incident," said a spokesperson for the United Shipbuilding Corporation.

The Investigative Committee, Russia's top criminal investigation agency, said it had launched a probe into alleged safety violations during repair works that triggered the blaze.

Local media report that the blaze on the 155m-long (500ft) submarine began when some insulation material caught fire during welding work.

Negligence and violation of safety rules were blamed for other Russian nuclear submarines that have been damaged by fires during repair works.

In December 2011, a fire broke out on the Yekaterinburg submarine in dry dock for repairs. It took fire crews about 20 hours to totally extinguish the blaze. Seven crew members were treated for inhaling poisonous fumes from the fire.