(Reuters) - The U.S. ambassador to South Korea left a Seoul hospital on Tuesday, five days after he was slashed by a knife-wielding Korean nationalist with a history of violent protest, causing wounds that required 80 stitches to the envoy's face.

Police are seeking to bring charges including attempted murder against Kim Ki-jong, 55, for the attack at a forum discussing Korean reunification. The ambassador, Mark Lippert, suffered a deep facial gash and a puncture wound on his wrist.

Lippert, 42, had become known for an approachable, informal style since taking up his posting in Seoul in November and the attack raised questions about his security arrangements.

The South Korean government has since ordered increased security for diplomatic missions, including the U.S. embassy.

"We have made it our mission to be open and friendly, and that will not change," Lippert told a crowded media conference amid heavy security at Yonsei University's Severance Hospital.

Lippert declined to comment on potential changes to his security arrangements. He said he expects to return to work as soon as possible and to make a full recovery.

"I feel pretty darn good, all things considered. I mean it was obviously a scary incident. But I'm walking, talking, holding my baby, hugging my wife, so I just feel really good," Lippert said.

Kim was given a suspended jail sentence in 2010 for trying to attack the Japanese ambassador by throwing a piece of concrete. He said after he attacked Lippert he was protesting against annual joint U.S.-South Korean military drills, which began last week.

Lippert was accompanied by his bodyguard, an unarmed South Korean policeman, when the attack took place at a government-owned theater across the street from the heavily guarded U.S. embassy. Other police were present at the event, although not at the request of the U.S. embassy or organizers.