U.S. envoy to South Korea Mark Lippert has suffered injuries on Thursday following a knife-wielding attack by an armed assailant in Seoul.

Lippert, who took office last year as the youngest envoy for the post, was slashed in his hand and cheek with a knife blade at 7:40 a.m. local time when he was preparing for a lecture at Sejong Cultural Center in central Seoul.

The assailant has been identified as Kim Ki-jong, 55, head of a South Korean progressive cultural activity group. Kim received a suspended two-year jail term in July 2010 for throwing two pieces of concrete at the Japanese ambassador to Seoul.

Kim shouted against the "war exercises," being held between South Korea and U.S., apparently indicating the annual military games code-named "Foal Eagle" and "Key Resolve" that kicked off Monday.

Lippert was taken to a nearby hospital to receive treatment on his cut in left hand and right cheek.

The White House has condemned the act of violence, saying that President Barack Obama had called Lippert and wished speedy recovery. It was the first attack against a U.S. ambassador to South Korea.

This act of violence might worsen the U.S.-South Korea alliance. Recently, there were worries over ties between Washington and Seoul as comments by U.S. Undersecretary of State Wendy Sherman on Japan-South Korea relations raised controversy.

The attack represented an anti-American sentiment shared by some South Koreans that hostile U.S. policy on the Democratic People's Republic of Korea (DPRK) might delay the reunification of the two Koreas.

After the attack, Kim told reporters that the U.S. would "restore its reason" by his act, saying the U.S.-South Korea war exercises have prevented Korean families, separated by the 1950-53 Korean War, from being reunited.

The "Foal Eagle" and "Key Resolve" military drills will continue as scheduled, according to a South Korean military official. The DPRK offered to suspend the war exercises in return for its halt of nuclear test in 2015, a proposal flatly rejected by Washington and Seoul.

South Korea's foreign ministry said that such an act of violence toward diplomatic missions will not be pardoned in any case. The ministry said it has taken the accident very seriously as it was done against the envoy of the U.S., "the most important ally" of the country.