US warns Russia over breaking truce in Ukraine

US Vice President Joseph Biden has warned Russia of imposing costs upon itself over what he called Moscow's continuing violation of a ceasefire deal with eastern Ukraine.

Ukrainian President Petro Poroshenko during a telephonic conversation with Biden informed him about "Russia's blatant escalation of the situation in eastern Ukraine, including increased shelling of Ukrainian government positions and the transfer of additional heavy weapons to the separatists," Xinhua reported citing a statement issued by the White House.

Biden said, "If Russia continued to wilfully violate the terms of the Minsk agreement, the costs to Russia will increase".

The deal, inked between Ukraine and the pro-Russian rebels Sep 5 in the Belarussian capital city of Minsk, was aimed at de-escalating the tension in eastern Ukraine and facilitating the release of hundreds of prisoners-of-war.

Russia has rejected the allegation that it is aiding the rebels in the conflict.

The tension, which escalated sharply since Ukrainian authorities decided to repeal the law which grants "special status" to the rebel-held Donetsk and Luhansk regions last week, has raised fear about a disruption of the prisoners-of-war swap.