SEOUL (REUTERS) - A South Korean army helicopter crashed during a test flight on Monday (Feb 15) morning, killing three soldiers, the country's Defence Ministry said.

All four crew members aboard were severely injured and three of them later died in hospital, a ministry official said.

The crash of the Bell UH-1H Iroquois helicopter took place at around 10am local time in the eastern city of Chuncheon, about 110km from Seoul.

Officials are investigating the cause of the crash.