European buyers of Russian gas faced a deadline to start paying in roubles on Friday, while negotiations aimed at ending the five-week war were set to resume even as Ukraine braced for further attacks in the south and east.

Moscow's invasion of its neighbour has killed thousands, sent millions fleeing and galvanised the United States and allies around the world to impose punishing penalties on Russian government entities, businesses and oligarchs.

Russia will respond to European Union sanctions...