PHNOM PENH (AFP) - Four Cambodian soldiers died and one was injured on Monday in a helicopter crash during military training on the outskirts of the capital, officials said.

The chopper exploded in mid-air at around 9.15 am (0215 GMT) before crashing into a water-filled quarry in Prey Sar village, around 10 kilometres from downtown Phnom Penh, police said.

"We now know that five soldiers were on board the helicopter. Four were killed and one was injured," Defence Minister Tea Banh told reporters at the crash site, revising an earlier death toll of five.

A 300-strong rescue team comprised of police, soldiers and divers searched for bodies at the quarry where an investigation into the cause of the accident is under way, said an AFP reporter at the scene.

"It appears that the helicopter exploded in the air before it crashed," military police spokesman Kheng Tito told AFP, adding the crash could have been caused by a technical issue or pilot error.

Soldiers were seen retrieving floating segments of the wreck, which was fully submerged in the water, but no bodies had been recovered.

Two military generals - including the commander of the air force's helicopter unit - were among the dead, Tito said.

Chuon Narin, Phnom Penh's deputy police chief, also said the chopper exploded before it crashed.

The surviving soldier is being treated for injuries at a hospital in the capital, he added.

The helicopter was one of 12 Z-9 choppers Cambodia bought from China last year to boost its military capacity.

In 2008, Cambodia's chief policeman Hok Lundy was killed in a helicopter crash along with the then deputy army commander and two pilots when their chopper went down in bad weather.