All 70 crew members of a Chinese conventional submarine have died in an accident, the official Xinhua news agency reported on Friday.

The No 361 submarine was taking part in a drill east of the the Neichangshan islands when the unexplained accident occured. Military chief Jiang Zemin has not commented publicly, but it is well known that many of China's stock of submarines are relatively old. 

The agency reported that the accident was caused by mechanical problems during training exercises in Chinese territorial waters, where manoeuvres have been staged in recent days. Xinhua has not given any further details or a specific date for the loss of life.

A Chinese Xia class conventional submarine is
about the same size as the Ming class

It was one of the worst naval accidents in Communist China's history, a military source said.

"Unfortunately, all 70 men and officers aboard the submarine died," Xinhua said. The submarine has been towed to an unidentified port.

Military analysts said the submarine, No. 361, was an indigenous Ming-class vessel, which usually has a coningent of nine officers and 46 men. The death toll of 70 raised a question, one military analyst  said.

"That's a lot of dead people for one submarine," said Wendell Minnick, a Taipei-based military expert.

"It's very strange, particularly that 70 died," he said. "Where did the extra 15 come from?"

Xinhua made no mention of any salvage work, indicating the
submarine had not sunk, and, presumably, the 70 men had not drowned.

"I don't believe it was under water," Minnick said. "A fire
or a collision is a possibility. If it was a torpedo that blew
up, it would have probably sunk it."

Military analysts speculated the crew may have been killed
by a poisonous gas leak, perhaps carbon monoxide from its
diesel engines. "It could have been toxic gas," a Beijing-based
Western diplomat said.

China has 13 Ming-class diesel submarines, which can go
without resupply for 60 days, according to Jane's Defence
Weekly.

The Chinese navy has suffered relatively few fatal accidents in recent times, unlike its Russian neighbours. However, in the mid-1980s, a destroyer exploded near the southern island province of Hainan killing nearly 100 people. 

China was believed to be negotiating with Russia last year to buy eight 636 kilo-class vessels, equipped with anti-ship missile systems, in a 1.6 billion dollar deal. 

According to reports, China's own submarine manufacturing
programme is in difficulty, particularly its efforts to develop the Song class guided-missile submarine. 

Jane's Defence Weekly says the first Song started sea trials in 1995 but proved a failure. China's navy has also reportedly
experienced operating problems because of inadequate crew training. 

Beijing hiked military spending 17.6 percent in 2002 to 169 billion yuan (20 billion dollars), but according to a white paper spending is still relatively low compared with developed countries.