By Li Hongmei

A US military helicopter crashed Tuesday near the border of the Democratic People's Republic of Korea (DPRK), a South Korean defense official said, with no reported casualties.

The helicopter, identified by South Korea's Yonhap news agency as a UH-60 Black Hawk, came down in Cheolwon county, which touches on the border with the DPRK.

The precise cause of the crash was not immediately clear, but the incident occurred during ongoing South Korea-US joint military exercises.

Yonhap quoted emergency rescue workers as saying the 12 service personnel on board the helicopter had survived the crash, which comes at a time of heightened military tensions on the Korean peninsula.

Pyongyang has condemned the joint exercises as a rehearsal for invasion, and made a series of dire threats of military retaliation.

There are 28,500 US military personnel permanently stationed in South Korea.