Russia-backed separatists walk after inspecting destroyed Ukrainian army tanks for  functional weapons and ammunition near the village of Lohvynove, outside Debaltseve, Ukraine, Sunday, Feb. 22, 2015, on the edge of the territory under their control....
FILE - Russia-backed separatists walk after inspecting destroyed Ukrainian army tanks for functional weapons and ammunition near the village of Lohvynove, outside Debaltseve, Ukraine, Feb. 22, 2015.

NATO Secretary-General Jens Stoltenberg has welcomed the withdrawal of Ukrainian and Russia-backed separatist forces from a frontline area in eastern Ukraine, but reiterated calls for Moscow to "withdraw all their troops."

"We welcome all efforts to reduce tensions," Stoltenberg said during a visit to the Ukrainian port city of Odesa on Wednesday, adding that "there is a long way to go because there are still cease-fire violations."

"NATO states very clearly that Russia has a special responsibility to... withdraw all their troops, all their officers" from eastern Ukraine, he added.

Stoltenberg's comments come a day after Ukrainian government troops and the separatists started a disengagement process in the town of Zolote in the eastern Ukrainian region of Luhansk.

Ukrainian armed forces have been fighting the separatists in Luhansk and the neighboring Donetsk region in a conflict that has killed more than 13,000 people since April 2014.

Under a deal reached earlier this month to end the five-year conflict, the sides agreed to start withdrawing from their positions in Zolote and the nearby town of Petrivske.

Ukrainian Foreign Minister Vadym Prystayko voiced hope on October 29 that Ukrainian President Volodymyr Zelenskiy would meet his Russian counterpart, Vladimir Putin, next month for peace talks mediated by the leaders of France and Germany, in what is known as the Normandy format.

Putin's aide Vladislav Surkov also welcomed steps to resume the disengagement of forces in eastern Ukraine, telling the TASS news agency: "If everything works out in Zolote, similar procedures in Petrivske should follow immediately. And after that, preparations may begin for another Normandy Quartet summit."

On October 30, Stoltenberg and the ambassadors from NATO's top decision-making body – the North Atlantic Council – arrived in Odesa for a two-day trip, and visited four vessels – from Bulgaria, Italy, Romania, and Spain – that are conducting patrols in the Black Sea.

Meeting with Ukraine's Deputy Prime Minister Dmytro Kuleba, Stoltenberg highlighted the Western military alliance's "support for Ukraine’s ambitious reforms, including in defense and security," according to a NATO statement.

"The visit today sends a clear message that NATO stands in solidarity with Ukraine," Stoltenberg said.