A senior presidential aide left for Vietnam to give support to former Prime Minister Lee Hae-chan after he suffered a heart attack during an official visit to Ho Chi Minh City.

Cho Jung-sik, President Lee Jae Myung's special adviser on political affairs, departed from Incheon International Airport at around 9:20 a.m. Saturday.

The president decided to send the adviser on Friday to receive a more comprehensive briefing on the situation as the former prime minister reportedly remains in critical condition after going through a coronary stent procedure.

Lee Hae-chan, who currently serves as the executive vice chairperson of the Peaceful Unification Advisory Council(PUAC), collapsed in Ho Chi Minh City on Friday after experiencing breathing difficulties.

He reportedly received cardiopulmonary resuscitation as he was being transferred to the emergency room.

A seven-term liberal lawmaker, Lee was the education minister during the Kim Dae-jung administration and the prime minister during the Roh Moo-hyun administration.