Leonid Kravchuk, who led Ukraine to independence amid the collapse of the Soviet Union and served as its first president, has died, a Ukrainian official said Tuesday. He was 88.

Andriy Yermak, head of President Volodymyr Zelenskyy’s office, confirmed Kravchuk’s death on the social media app Telegram without giving details of the circumstances. Kravchuk had been in poor health and underwent a heart operation last year.

Kravchuk led Ukraine as its Communist Party boss in the waning years of the Soviet Union, and played a pivotal role in the demise of the USSR before holding the Ukrainian presidency from 1991 through 1994.

As president Kravchuk agreed to transfer remaining Soviet nuclear weapons on Ukrainian territory to Russian control in a deal backed by the United States.