A major fire aboard a docked Russian nuclear submarine that injured seven crew members with toxic fumes and left others stuck inside the vessel appeared to be brought under control on Friday, and officials said the blaze had caused no radiation leaks.

The fire began on Thursday at an Arctic shipyard where the submarine Yekaterinburg was in drydock. At midday on Friday, Russian state television showed the rubber-coated hull of the submarine still smoldering, with firefighters gathering around it and some standing on top to douse it with water.

An unspecified number of crew have remained inside the submarine, Defense Ministry spokesman Col. Igor Konashenkov said in a statement. He insisted there was no danger of fire spreading inside the sub and said the crew has reported that the conditions on board have remained normal. Konashenkov's statement left it unclear whether the crew were trapped there or ordered to stay inside.

The Defense Ministry and the Foreign Ministry said there has been no radiation leak from the fire.

The Norwegian Radiation Protection Authority said it has received information from both civil and military authorities in Russia that there was no radioactive leak. The Norwegian agency said it has not measured any increased radioactivity, adding it is following the situation closely.

However, the governor in Finnmark, Norway's northeastern province that borders Russia's Murmansk Oblast, told Norwegian broadcaster NRK that he was disappointed with Russia's response.

"There have been problems to get clear information from the Russian side:" Gunnar Kjoennoey was quoted as saying. "We have an agreement to exchange information in such cases, but there has been no information from the Russian side so far."

Russia's military says the blaze started on wooden scaffolding and then engulfed the sub's outer hull. It said the vessel's nuclear reactor had been shut down and its nuclear-tipped missiles and other weapons had been unloaded before the repairs.

Toxic fumes from the blaze had spread to the town of Roslyakovo where the shipyard is located, but officials said there was no need to evacuate local residents.

It would take a few more hours to fully extinguish the smoldering outer hull, Emergency Situations Minister Sergei Shoigu said during a midday meeting. He said seven members of the submarine crew have been hospitalised after inhaling poisonous carbon monoxide fumes from the fire.

The Yekaterinburg is a Delta-IV-class nuclear-powered submarine that normally carries 16 nuclear-tipped intercontinental ballistic missiles. It was built in 1984.

Most modern submarines' outer hulls are covered with rubber to make them less noisy and more difficult for an enemy to detect.

The chief of the General Staff of the Russian armed forces, Gen. Nikolai Makarov, led a team of senior military officials to Roslyakovo to oversee the rescue efforts.

Military prosecutors have launched an investigation into a possible breach of safety regulations that led to the fire. President Dmitry Medvedev summoned top Cabinet officials to report on the situation and demand a punishment for any culprits.