Ukrainian President Petro Poroshenko has held a telephone conversation with U.S. Vice President Joseph Biden, the Ukrainian president's press service reported.

According to the report, the parties expressed concern over the murder of Russian opposition leader Boris Nemtsov.

Poroshenko and Biden also agreed about the further coordination of the joint efforts towards Donbas settlement.

The two sides stressed that the world today should stand united with Ukraine not only in the matter of territorial integrity, but also in freeing Ukrainian pilot Nadia Savchenko, whose state is critical.