Kazulin is serving a jail term of 5 1/2 years for antigovernment protests in March.
He began his hunger strike to protest his jail term and to draw international attention to the authoritarian regime of President Alyaksandr Lukashenka.
In an open letter to the leaders of major world powers made public today, Belarusian opposition leader Alyaksandr Milinkevich said Kazulin's physical state was "almost at an end."
Milinkevich also said Kazulin would end his hunger strike "if just one G-8 nation were to declare its intention to discuss the human rights situation [in Belarus] at the UN Security Council."
(Charter 97, dpa)