Mark Lippert's injuries are not life-threatening, media reports say
US ambassador to South Korea Mark Lippert has been injured by an attacker in Seoul, officials say.
The attack happened as Mr Lippert, 42, was about to attend a breakfast meeting in the capital.
Pictures later emerged showing the envoy bleeding from his face and left hand. He was cut by a razor blade.
Mr Lippert was taken to hospital. The attacker - believed to be a 55-year-old man - was subdued by security officers and arrested.
Mr Lippert's injuries were not life-threatening, the US State Department said.
The attack happened at about 07:40 (22:40 GMT Wednesday), as the ambassador was entering a lecture hall in central Seoul, South Korean police were quoted as saying by the Yonhap news agency.
The attacker was arrested by security officers in central Seoul
The ambassador was due to attend a breakfast meeting in central Seoul
The assailant reportedly shouted "South and North Korea should be reunified!" before lashing out at the envoy.
The attacker also expressed his opposition to annual military exercises held jointly by South Korea and the US, which are currently under way.
North Korea has described the exercises - which involve more than 200,000 troops - as a rehearsal for an invasion and has vowed retaliation.
However, there is no evidence that the attacker was an agent of North Korea, the BBC's Stephen Evans in Seoul reports.
Some South Koreans believe that the American military presence prevents unification of the two Koreas, our correspondent adds.
The assailant had previously thrown concrete at the Japanese ambassador to South Korea. He also has a record of militant Korean nationalistic activism.
US President Barack Obama later called Mr Lippert to wish him "the very best for a speedy recovery", US National Security Council spokeswoman Bernadette Meehan said.
Meanwhile, the US state department said: "We strongly condemn this act of violence."
Mr Lippert - a former US assistant secretary of defence - was appointed ambassador to South Korea in 2014.
His wife gave birth in the country, and the couple gave their son a Korean middle name, according to the Associated Press news agency.