Ukraine on Saturday denied claims that it had refused to negotiate with Russia to put an end to the conflict, Ukraine’s UNIAN news agency reported.

"This is not true, we are open to realistic proposals to deescalate the conflict," an official at the Ukrainian presidency was quoted as saying.

Earlier, Kremlin spokesperson Dmitry Peskov said "the Ukrainian side has refused to negotiate" and Russian forces resumed their advance in accordance with the operational plan.

Russian President Vladimir Putin announced a "special military operation" in Ukraine on Thursday, days after recognizing two separatist-held enclaves in eastern Ukraine.

In a televised address, Putin said the people of Donbass asked Russia for help, claiming that he wanted to "demilitarize" and "denazify" Ukraine.

Fighting on the third day of the attack is said to have reached the streets of Ukraine’s capital Kyiv.

Ukraine's Interior Minister Denys Anatoliyovych Monastyrsky said over 25,000 weapons and millions of rounds of ammunition were distributed to military volunteers in Kyiv.

Earlier, Ukrainian President Volodymyr Zelenkskyy had signed a decree on general mobilization of the population. Conscripts and reservists will be called up over the next 90 days to "ensure the defense of the state, maintaining combat and mobilization readiness."

Russian units in Ukraine were ordered to resume their offensive from all directions after a pause Friday.