Initial inquiries suggested the Russian-made MI-8 helicopter had hit a military communications mast on the island of Me, around 10 kilometres (six miles) off the coast of Thanh Hoa province, some 200 kilometres south of Hanoi.

"The helicopter immediately exploded after hitting the pylon" shortly after taking off on Wednesday afternoon, military spokesman Major Pham Xuan Huong said.

The spokesman identified the dead as 12 officers, a military journalist with the rank of captain and the three pilots.

One of the generals was the commander of Vietnam's military zone number four based in the central province of Nghe An. Among the other dead officers were five colonels, three lieutenant colonels and two majors.

The state-controlled Vietnam News Agency said the senior officers were inspecting "the combat readiness in the region".

"More or less all the staff of the fourth zone died in the crash. The chief was there, with his deputy and the commanders of all the bureaus," a foreign military source told AFP.

The army spokesman said the bodies of all the victims had been recovered. The defence ministry has opened a formal investigation into the cause of the crash.

A Vietnamese source said the insurance company in charge of the military fleet of this zone had refused to insure the helicopter that was allegedly in poor condition.

The Vietnamese army has constantly reduced its budget and forces since the end of the Vietnam War in 1975.

The foreign military source said he had no details about the cause of the crash but confirmed the Vietnamese army had some problems with spare parts.

"For a long time Vietnam was getting its spare parts through the countries of the Warsaw Pact. But since the fall of the Berlin wall, they have to buy them at market price", he said.

"You have also to question maintenance. How is it organized? Is it done properly?" he asked.

According to sources, Vietnam has recently bought some modern helicopters but much of its fleet is old.

In May 1998, Vietnam's chief of staff and deputy defense minister, general Dao Trong Lich, died when a Laos airforce jet slammed into a mountain in the Laos province of Xienkhouang. Fourteen Vietnamese on board, including several other top officials died, leaving a huge gap in the military to fill.

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