SEOUL -- A military drone and a helicopter crashed at an army airfield in South Korea Monday, without any casualty, according to local broadcaster YTN and Yonhap news agency.

It was reported at around 1:00 pm local time (0400 GMT) that the drone crashed into the helicopter, which landed at the airfield in Yangju, about 30 km north of the capital Seoul.

The drone and the chopper were destroyed after catching fire, but no casualty was reported.

The authorities were investigating the cause of the accident.