"The fire was extinguished around midnight Moscow time" (2000 GMT Wednesday), Interfax news agency quoted a northern fleet press officer as saying.

"The submarine's nuclear energy protection apparatus was activated. There is no kind of nuclear contamination threat," he said.

The submarine, the Saint Daniel of Moscow, was on the surface of the Barents Sea north of the Rybachy peninsula at the time of the fire late Wednesday.

The two victims, aged 35 and 28, were asphyxiated by burning material from the submarine's interior, said the navy's top admiral, Vladimir Masorin, on Russian television.

They were taken out of the submarine still alive but died during efforts to resuscitate them.

A third man who came to their aid suffered non-fatal poisoning, he said.

They "apparently didn't have time to connect their respiration apparatus," Masorin told ITAR-TASS.

A fleet spokesman said that the fire had broken out "due to a short-circuit in the energy supply system in one of the nose sections".

There have been at least five incidents involving Russian nuclear submarines since 1992, including what authorities said was "a serious incident" aboard a Delta IV-class vessel equipped with intercontinental missiles, and the wreck of the K-159 submarine in the Barents Sea, killing nine.

But the biggest catastrophe was the sinking of the Kursk in August 2000, also in the Barents Sea not far from the northern fleet's headquarters at Severomorsk.

That incident, triggered by the explosion of a torpedo aboard the Kursk, claimed the lives of all 118 on board and focused attention on the riskiness of Russia's ageing fleet, as well as government attempts to cover up the news.

Following the latest incident, the Saint Daniel of Moscow was towed to Vidyayevo, near Severomorsk.

Masorin said the 16-year-old vessel had exceeded a deadline by which renovation work was due.

In a statement, Russia's prosecutor general's office said it had opened an investigation for "violation of a ship's rules of conduct".

At 107-metres (350-feet) in length, the Victor IV-class submarine was designed to carry 96 people, as well as cruise missiles, mines and torpedoes.

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