South Korea's former Ambassador to the US Hyun Hong-choo, noted for his active role in expanding Seoul's diplomatic frontiers in the 1980s-1990s, passed away Saturday. He was 76.

The cause of his death is not immediately known. A memorial altar for him is set up at Asan Medical Center in Seoul.

Hyun, who served as Seoul's top envoy to the US from 1991-1993, has transcended the fields of politics, diplomacy, academia, government administration and the prosecution with his expertise, experience and wide personal connections, observers said.

Hyun is best remembered for his contribution to gaining UN membership for the two Koreas in the early 1990s and implementing former President Roh Tae-woo's signature foreign policy, dubbed "Nordpolitik." Roh led the country from 1988-1993.

Under the policy drive, South Korea established diplomatic ties with Hungary, Poland and Yugoslavia in 1989. It also opened relations with Czechoslovakia, Bulgaria and Romania in 1990 and with Albania the following year.

During the Roh government, Hyun served as the government legislation chief in 1988, ambassador to the United Nations in 1990 and then ambassador to the country's chief security ally, the US.

In 1993, he started working as a private lawyer handling international trade, investment and other legal affairs. After passing a state bar exam in 1963, he served as state prosecutor for a decade from 1968.

During the Lee Myung-bak administration from 2007-2013, Hyun served as a member of the presidential advisory panel on national reunification and of the presidential committee on national security. In 2013, he was appointed as chair professor of the Korea National Diplomatic Academy attached to the foreign ministry.

Hyun graduated from the law college of Seoul National University in 1963. In 1969, he obtained a master's degree in law from Columbia University.

He is survived by his wife and three children. (Yonhap)