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

Media images showed a stunned-looked 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 center in Seoul as the ambassador was preparing for a lecture, and said Lippert was being treated at a local hospital and his injuries weren't life threatening.

YTN TV reported that the man -- identified by police as a 55-year-old, surnamed Kim -- screamed during the attack, "South and North Korea should be reunified."

The suspect also shouted anti-war slogans after he was detained, and Seoul police say the weapon used had a 25-centimeter blade.

Yonhap TV showed men in suits and ties subduing the attacker, who was dressed in a modern version of the traditional Korean hanbok, and Lippert later being rushed to a police car with a handkerchief pressed to his cheek.

The attacker's comments on Korean reunification seem linked to lingering, deep divisions in South Korea that stem from the Korean War. The rival Koreas have been divided for decades along the world's most heavily armed border. The U.S., which backed South Korea during the 1950-53 Korean War, still stations 28,500 troops in South Korea as a deterrent against North Korea, and some South Koreans see the U.S. presence as a barrier toward a reunified Korea.

Anti-U.S. protesters have recently been demonstrating to voice opposition to annual U.S.-South Korean military exercises that North Korea says are preparation for an invasion. Seoul and Washington say the drills, which will run until the end of April, are defensive and routine.

Lippert, 42, became ambassador last year and has been a regular presence in Seoul and social media during his time in Seoul. His wife gave birth here and the couple gave their son a Korean middle name. Lippert was formerly the U.S. Assistant Secretary Defense for Asian affairs and a foreign policy aide to President Barack Obama when Obama was a U.S. senator.

Obama called Lippert after the attack to express his thoughts and prayers for a speedy recover, the White House said.

"We strongly condemn this act of violence," State Department spokeswoman Marie Harf said. She had no other details.