One year ago Sunday, the Russian nuclear submarine Kursk exploded and sank in the Barents Sea in the Russian Arctic. Despite the passage of time, many questions remain unanswered about just what happened on the submarine.

Family members of the 118 crewmen who perished on the Kursk are gathering to mark the anniversary in the town where the submarine was based.

For most of the relatives, the passage of time has done little to help them overcome grief at the loss of their loved ones.

There also is anger at the slow and secretive way the authorities responded to the disaster. People still ask why two days passed before the government even admitted that something had happened, and then only after Western seismologists said they had detected two large underwater explosions.

They also wonder why it took another two days before the authorities asked for outside help in trying to reach the sunken vessel and rescue any survivors.

At the time, President Vladimir Putin came under a storm of criticism for failing to interrupt his beach vacation after hearing of the accident. On Friday Mr. Putin awarded a medal posthumously to the captain of the Kursk, handing the medal to the officer's widow. Afterward she said the president talked at length with her about the accident and praised her husband.

But many other widows remain bitter at the Russian president and senior navy officials. One woman who lost her son has brought a lawsuit against the navy's senior commander, accusing him of murder.

Many relatives say the Kursk was testing a new torpedo propulsion system when one of the weapons exploded, causing the vessel to sink.

Some top navy and government officials continue to maintain that the Kursk collided with another submarine or some other object, despite any evidence to back up this theory.

A third explanation is that another Russian ship fired a missile accidentally at the Kursk, which was taking part in special naval exercises when the accident occurred.

The anniversary comes as divers continue working at the disaster site with preparations to raise the wreck of the Kursk next month.