Russia will attempt to destroy Ukraine and change its borders, Polish Prime Minister Mateusz Morawiecki said on Wednesday commenting on a partial mobilization announced by Moscow.

"We will do all we can with our allies, so that NATO supports Ukraine even more so that it can defend itself," Morawiecki said, urging more help for Kyiv from western allies.

Russian President Vladimir Putin on Wednesday called up 300,000 reservists to fight in Ukraine and said Moscow would respond with the might of all its vast arsenal if the West pursued what he called its "nuclear blackmail" over the conflict there.

"The reports about partial mobilisation have been confirmed, Russia will attempt to destroy Ukraine and grab some of its territory. We can't allow for that," Morawiecki said during military drills the Polish army held with U.S. and British allies in eastern Poland.

(Reporting by Marek Strzelecki, Pawel Florkiewicz and Anna Koper; Editing by Andrew Cawthorne and Alison Williams)