Ukrainian President Volodymyr Zelenskiy said he had discussed further support of Ukraine's armed forces by NATO member states, in a call with the bloc's Secretary General Jens Stoltenberg on Tuesday.

The phone call came in the wake of votes staged in four occupied regions of Ukraine on annexation by Russia.

Zelenskiy thanked Stoltenberg for his condemnation of the votes, which Ukraine and its western allies call illegal shams.

"We discussed current battlefield developments and further support of the Alliance’s member states to the Ukrainian Armed Forces," Zelenskiy wrote.