A military helicopter crashed near a residential area in South Korea's eastern region, leaving three crew members dead and one seriously injured, authorities said Monday.

The Army's UH-1H helicopter crashed into a field next to its base in Gangwon Province at around 10:10 a.m. while conducting a checkout flight, according to police and firefighting authorities.

While all four crew members were rushed to nearby hospitals, three, except for the pilot, were later pronounced dead, military officials said. The 50-year-old pilot is in critical condition, though he is still conscious.

Authorities said there were no reports of damage or human casualties from the civilian side. The chopper was completely destroyed.

"The aircraft had a flight schedule planned after the test operation," a military official said.

The military and firefighting authorities said they are investigating to determine the exact cause of the accident. (Yonhap)