SEOUL - South Korean former president Roh Tae-woo, a decorated war veteran who played a pivotal but controversial role in the transition to democratic elections from rule by authoritarian leaders, has died, a Seoul hospital confirmed.

The 88-year-old died on Tuesday (Oct 26), a Seoul National University Hospital official said, without citing the cause of death.

Roh had been in poor health since 2002 when he received surgery for prostate cancer and he was repeatedly hospitalised in recent years.

In the space of a few decades, Roh went from military coup conspirator to South Korea's first popularly elected president, before ending his political career in ignominy with a jail sentence for treason and corruption.

"I now feel limitlessly shameful for being a former president," Roh told the public in a tearful televised apology in 1995 for secretly amassing a US$654 million (S$881 million) slush fund while in office.

Roh was born on Dec 4, 1932, the son of a poor farmer in Talsong County, near the southeastern city of Taegu. He was educated first at the Korean Military Academy in Seoul and later attended a psychological warfare course at Fort Bragg, North Carolina.

Roh began his military career during the 1950-1953 Korean War and was the commander of a combat unit in the Vietnam War.

When former strong man Park Chung-hee was assassinated in 1979, Roh supported his former military classmate Chun Doo-hwan in a military coup that installed the latter in the presidential Blue House. Roh was rewarded with a series of government posts.

However, when Chun named Roh as his successor ahead of the 1987 presidential elections there was a public outcry, with large pro-democracy rallies held in Seoul and other cities.

In response and to distance himself from Chun, Roh issued the "June 29 Declaration," announcing significant political reforms including the direct election of the president.

He campaigned as a man of the people. In office, he discarded the title "excellency" and opened up the Blue House to the public.

Roh had success as a global statesman, scoring a diplomatic breakthrough with his "Nordpolitik" drive to establish formal ties with Cold War-era enemies Russia and China.

As the original driving force behind the 1988 Seoul Olympics, Roh helped South Korea forge a new international identity. He also ushered the country into the United Nations in 1991.

But his term in office was blighted by street protests and economic instability. Two weeks before he left the Blue House he was voted the worst politician in South Korea in a public survey.

Just a few years later he was sentenced to 22 and half years in prison for his role in the 1979 coup and the 1980 Gwangju army massacre of pro-democracy demonstrators, as well as massive corruption.

Grim-faced and wearing prison pyjamas, Roh faced court alongside Chun, who received a commuted death sentence. Local media dubbed it the "trial of the century" as it dug up many of the dirtiest secrets from South Korea's era of strongman rule.

Referring to the massacre, the judges' verdict accused Chun and Ro of "putting down popular resistance to clear the way for their rise to power".

Female relatives of the Kwangju victims, dressed in traditional mourning white, attacked Roh's son, Jae-hun, as he left the court, shouting "kill the murderer's son."

Both men were pardoned by President Kim Young-sam and freed from jail in 1997.In 2013, Roh's family helped him pay off the last of the money he illegally amassed during his presidency.

Roh is survived by his wife Kim Ok-sook and his two children. Son Roh Jae-heon is a certified lawyer in New York state and the president of the East Asia Culture Centre in Seoul. Daughter Roh Soh-yeong, a director at an art museum in Seoul, is in the middle of a high-profile divorce trial with Chey Tae-won, the chairman of conglomerate SK Group.