Singapore's second longest-held political detainee, Dr Lim Hock Siew, has died at the age of 81.
The Straits Times reported that he is believed to have died on Monday night.
The founding member and leader of Barisan Sosialis, the party formed by a splinter group of the People's Action Party in 1961, had previously suffered from kidney failure in 2009.
Dr Lim was among the 110 leftists and unionists arrested on Feb 2, 1963. They were imprisoned under a government security exercise called Operation Cold Store which targeted suspected communists.
The paper reported that ten years before he was released, he said that the Internal Security Department had indicated he would be released if he issued a statement saying he would give up politics and concentrate on his medical practice instead. He was also asked to say he supported the parliamentary democratic system, said ST.
He refused to do so and demanded an unconditional release instead.
He said: "The fact that I had been detained for over nine years in order to coerce me to give up politics is proof enough that there is no parliamentary democracy."
He remained in detention for about twenty years without a trial until he was finally released on Sept 6, 1982.