SEOUL -- Lee Hae-chan, a former South Korean prime minister who was serving as a senior vice president of the Peaceful Unification Advisory Council (PUAC), died on Sunday while receiving medical treatment in Vietnam, Yonhap News Agency reported.

Lee collapsed on Jan 23 during a business trip to Ho Chi Minh City, where he was attending a meeting of the council's Asia-Pacific regional committee, and was rushed to a local hospital, according to Yonhap.

He was diagnosed with an acute myocardial infarction and underwent a stent procedure by local medical staff, but failed to recover and passed away at 2:48 pm local time.

A seven-term lawmaker and a veteran figure of South Korea's democratic movement, Lee served as prime minister under former President Roh Moo-hyun from 2004 to 2006.