The U.S. ambassador to South Korea, Mark Lippert, has been injured in an attack by an armed assailant in Seoul.
Local media reports said Lippert has been transported to a hospital for treatment.
Lippert, 42, was bleeding from a facial wound, but was walking after the attack as he was taken to the hospital, news reports said.
Reports said Lippert was slashed on his right cheek with a razor blade. The extent of his injuries is not known.
Appearing on CNN, State Department spokeswoman Marie Harf said Lippert is now in the hospital and they have yet to determine a motive.
"We will do a full investigation," Harf said, adding that his "injuries are not life threatening."
Yonhap news agency said a man only identified by his surname, Kim, was arrested after the attack. It said the man screamed "South and North Korea should be reunified'' during the attack.
The rival Koreas have been divided for decades along the world's most heavily armed border. The U.S. has stationed 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 unified Korea.