Ukrainian President Volodymyr Zelensky has reiterated his call for Russian President Vladimir Putin to hold talks to stop conflict."Fighting is going on all over Ukraine. Let's sit down at the negotiating table," Zelensky was quoted by the Interfax-Ukraine news agency as saying on Friday.Putin said Moscow is ready to negotiate with Ukraine at a high level, Russia's RIA Novosti news agency tweeted on Friday.On Thursday, the Russian President authorised "a special military operation" in Donbas, Xinhua news agency reported.At least 137 Ukrainians were killed and more than 300 injured in the military operation, Zelensky said earlier on Friday.