Ukrainian President Volodymyr Zelensky has called Russian President Vladimir Putin to exchange New Year greetings and congratulations on the exchange of captives on December 29, the Ukrainian presidential administration said in a statement.

"The sides welcomed the contract for Russian gas transit via Ukraine, which was signed yesterday," the statement, which was published on Facebook, said.

Zelensky and Putin agreed to immediately start coordinating the lists of Ukrainians, including Crimean residents, incarcerated in Crimea and Russia, as well as Russians incarcerated in Ukraine.

They also expressed hope for the soonest implementation of a complete ceasefire on the Donbas contact line.