U.S. Ambassador Mark Lippert was slashed on the face and wrist by a man wielding a weapon with a 10-inch blade and screaming that the rival Koreas should be unified, South Korean police said Thursday.

Photographs obtained by the Associated Press showed a stunned-looking Lippert staring at his blood-covered left hand and holding his right hand over a cut on the right side of his face, his pink tie splattered with blood.

The U.S. State Department condemned the attack, which happened at a performing arts centre in downtown Seoul as the ambassador was preparing for a lecture.