Paek Ki-wan, an activist who devoted his life to the reunification of the two Koreas, democracy and labor rights, has died at the age of 88 on Monday.

According to Seoul National University Hospital, Paek had been hospitalized since January last year for symptoms of pneumonia.

Born in North Korea's South Hwanghae Province in 1932, Paek, whose family was separated during the Korean War, worked to educate the poor and farmers, and to reunify the divided Koreas.

In 1964, Paek protested against Seoul and Tokyo's signing of a treaty to normalize relations, and was imprisoned in 1974 for demonstrating against then-President Park Chung-hee's dictatorship.

The activist dropped out of the 1987 presidential race and was unsuccessful at a second presidential bid as an independent five years later.

Since then, he had established and led a research institute on unification, through which he had launched various social and labor campaigns.

He also wrote numerous novels, essays and poems, as well as the lyrics of "March for the Beloved," a famous pro-democracy movement anthem.