Russian President Vladimir Putin on Thursday accused the West of decades of aggression toward Moscow and warned that if it wanted to attempt to beat Russia on the battlefield it was welcome to try, but this would bring tragedy for Ukraine.

His remarks came as Russian Foreign Minister Sergey Lavrov prepared for a closed-door foreign ministers' meeting at a G20 gathering in Indonesia on Friday — the first time Putin's top diplomat will come face-to-face with the most vocal opponents of the invasion of Ukraine since it began in February.

Russian shells fell in eastern Ukraine ahead of an expected new offensive, while three were killed in the northeastern city of Kharkiv, authorities said.