The Kremlin has said Kiev has refused to hold talks with Moscow, causing Russian forces to resume operations in Ukraine.

"The Ukrainian side has refused to negotiate. This Saturday afternoon Russian forces have resumed their advance in accordance with the plan of the operation," Kremlin Spokesman Dmitry Peskov said on Saturday.

Russian President Vladimir Putin on Friday ordered a halt to military operations in light of the expected negotiations that were previously planned with Ukraine, local media reported citing Peskov.

Putin on Thursday authorised "a special military operation" in Donbas, and Ukraine confirmed that military targets across the country were under attack, Xinhua news agency reported.

On Saturday, Oleksiy Arestovich, Advisor to the Head of Ukraine's presidential office, said Kiev refused to negotiate with Russia because the conditions Russia proposed are "unacceptable" for the country, calling those conditions as "an attempt to force us to surrender."