Russian naval officers attended a remembrance service in Moscow

Flags were flown at half mast on all Russian navy vessels and sailors observed a minute of silence.

Church services were held in Moscow, St Petersburg and at the sub's Arctic home base of Vidyayevo. In the city of Kursk a new monument was unveiled.

Just days ago a Russian mini-sub's crew was rescued in the Pacific.

The dramatic intervention of a British rescue team to free the trapped Priz submersible and its crew of seven from the seabed brought back painful memories.

It raised questions about why, five years on from the Kursk, Russia still had no modern deep-sea rescue equipment.

The sinking of the Kursk - one of Russia's newest and most modern submarines - during exercises in 2000 was the country's worst peacetime military disaster.

Poignant monument

The 118 sailors who died were remembered with services on all Russian fleets.

The Kursk was one of Russia's most modern submarines

In pictures: Russia mourns

Relatives attended services in Moscow and St Petersburg, where many of the men are buried, local media reported.

They laid wreaths at the graves and flowers were cast into the sea at Vidyayevo.

In the central Russian city of Kursk, from which the vessel took its name, a monument made from fragments of the submarine was unveiled.

"For us, it's as if part of our boys were here," one woman told Russia's Channel One TV.

A small number of the crew survived the initial explosion of an unstable torpedo - only to die hours later, slowly suffocating in freezing conditions and pitch darkness.

A rescue mission of sorts had been launched but Russia refused foreign assistance, even though its navy lacked modern search-and-rescue equipment.

Many believe that 23 sailors who survived the blast might have been saved, had the Russian navy reacted in time.

Reforms delayed

The sinking was also a public relations disaster for the Russian navy and the Russian authorities.

The BBC's Steven Eke says live media reports of the incident, which happened early in Mr Putin's presidency, helped shape Russia's current leadership.

Analysts say the negative coverage was one of the key factors in the way the Kremlin went on to wrest back control of Russia's TV channels.

There could be no admission of impotence, our correspondent says, and none of the offers of resignation from navy officers were accepted.

Even the unprecedented government inquiry into the disaster decided no blame or responsibility could be apportioned, he adds.

Military prosecutors closed their investigation in July 2002, concluding that no sailors could have lived long enough after the explosion to be rescued.