The two pilots who were on board the chopper are known to be in a stable condition.

The accident occurred around 11:46 a.m. when the chopper got stuck on a high-tension power line during a mission to put out a fire that has ravaged the country's eastern areas, according to officials.

The helicopter was partially damaged in the process of making the landing alongside a stream, they said.

Tens of fire-fighting helicopters and thousands of people have been mobilized to contain the fire that began Saturday.

Authorities said they are investigating the details of the incident.

Meanwhile, the Army said it has expanded the size of troops to support efforts to bring the blaze under control.

More than 6,300 soldiers and 11 choppers were in operation at the site as of 1 p.m. Monday, an increase of some 700 troops and seven copters from earlier in the day.

"We are carrying out a mission to put out the fire by pouring water from buckets attached to helicopters," an Army official said.

The Air Force has also dispatched around 430 service members and four choppers for a similar operation. (Yonhap)