Denis Pushilin, the self-declared leader of the radicals in Donetsk, told reporters on April 18 that he did not consider his men bound by a compromise agreement between Russia and Ukraine to disarm and vacate occupied buildings.
The agreement was reached at four-party talks on April 17 in Geneva also involving the United States and the European Union.
Pushilin said the government in Kyiv was illegitimate and also must vacate public buildings that he said it was occupying illegally.
Local media reports on April 18 said none of the government buildings seized across eastern Ukraine had yet been vacated.
Ukrainian Prime Minister Arseniy Yatsenyuk told parliament on April 18 that the government had drafted a law that would offer an amnesty to insurgents who would lay down their arms and leave the occupied buildings.
The government has said the amnesty would not apply to protesters accused of committing serious crimes.
Yatsenyuk also told parliament his government did not hold "unreasonable" hopes for the Geneva agreement.
WATCH: Thousands attended a pro-Ukrainian rally the eastern city of Donetsk on April 17 despite security worries as armed separatists continued to occupy government buildings in the Donbas region. (RFE/RL's Ukrainian Service)
U.S. President Barack Obama expressed cautious optimism over the agreement but warned that the United States and its allies were ready to impose new sanctions on Russia if the situation failed to improve.
Moscow denies accusations by Ukraine and the West that it has been orchestrating the pro-Russian protests in eastern Ukraine following Moscow's annexation of Ukraine's Crimea in March.