"Saddened by the passing away of Stanislav Shushkevich, the first & so far the only head of independent, democratic Belarus. His signature on the declaration dissolving the Soviet Union will live in history, his memory - in our hearts. Condolences to the family & #FreeBelarus," Simonyte tweeted on Wednesday.
The first leader of independent Belarus, who later became a critic of the country's authoritarian leader Alexander Lukashenko, died at the age of 87.
Speaking with AFP, his wife confirmed he died as a result of coronavirus-related complications.
In December, 1991, Boris Yeltsin, Leonid Kravchuk and Stanislav Shushkevich, the then leaders of Russia, Ukraine and Belarus, gathered in the Belovezhskaya Forest and declared the Soviet Union was defunct.