SEOUL: A North Korean mine which drifted along a river into the neighbouring South killed a man and badly injured another when it exploded, military officials said Sunday.

Several wooden box mines have been retrieved by South Korean soldiers and police, but it was not immediately clear how the mines ended up drifting into the South.

The explosion was reported shortly before midnight Saturday in a restricted border area in Yeoncheon, 60 kilometres (35 miles) northeast of Seoul, the defence ministry said.

A 48-year-old man died and a 25-year-old man was seriously injured.

"Han was killed by one of the North Korean wooden box mines which had drifted south along the border river," a ministry spokesman told AFP.

South Korean soldiers and police have retrieved 29 boxes of North Korean mines in their joint search which began on Friday along all streams connected to the Imjin River, he said, of which 18 boxes were empty.

Heavy rain has hit the northern part of the peninsula in recent weeks, swelling water levels. The North has discharged water from dams north of the river flowing to South Korea.

Last September six South Korean campers died when North Korea suddenly discharged dam water and created a flash flood.

Tensions remain high across the border after the South accused the North of torpedoing one of its warships in March.

BDST: 0912 HRS, August 01, 2010