Two North Korean border guards were attacked by unidentified assailants, leaving one dead and the other seriously injured, a U.S-based media report said Friday.

A source in North Korea's northern province of Ryanggang told Radio Free Asia that the pair were on guard duty at the Sino-North Korea border when they were attacked Sunday. It said the soldiers were patrolling the border area.

The source said the attackers, presumed to number two or more, struck them on the head with stones several times. The weapons used by the guards were left at the scene.

Following the incident, North Korean army units in the region were placed on emergency alert and told to find the perpetrators, according to RFA, adding that no arrests have been made.

The source said the location of the incident, near Hyesan city of Ryanggang Province, is frequented by smugglers and defectors. (Yonhap)