US ambassador to South Korea Mark Lippert waves as he leaves a hospital in Seoul March 10, 2015.[Photo/Agencies]

SEOUL - The US 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 US 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.