HANOI - FOUR men were killed when a Vietnam War-era bomb they were scavenging for metal exploded in central Vietnam, an official said on Wednesday.

Three farmers and a teacher, aged from 26 to 30, were killed on the spot when the 500kg bomb exploded on Tuesday night, said Truong Quang Than, chief of Huong Hoa village in Quang Binh province.

The men's metal detector found the bomb, they used a crowbar to test it and it exploded, Mr Than said.

The area was part of the Ho Chi Minh Trail, which was heavily bombarded by US planes during the Vietnam War to prevent movement of supplies, men and weapons from the communist North to the southern battlefields.

Unexploded ordnance left over from the war has killed more than 42,000 people and wounded some 62,000 in the country since the conflict ended in 1975, according to government figures. -- AP