Russian President Vladimir Putin has ordered Russian troops to withdraw to their permanent bases after military exercises in the Rostov region near the border with Ukraine, Russian news agencies reported late on Saturday, citing a Kremlin spokesman.

The troops pullout came before an expected meeting between Putin and his Ukrainian counterpart, Petro Poroshenko, in Milan, Italy, on Friday.

The Kremlin spokesman, Dmitry Peskov, said that the Russian president had met with Russian Defense Minister Sergei Shoigu.

"The minister had reported to the Supreme Commander about the completion of summer period of training on shooting ranges of the southern military district," Peskov said according to RIA Novosti news agency.

"After the report, Putin ordered to launch the return of the troops to their permanent bases. ... In total, these are 17,600 military servicemen who were trained on the shooting ranges of the Rostov region in summer," Peskov said.

Relations between Moscow and NATO are at a post-Cold War low since Russia's annexation of Crimea in March.

Putin and Poroshenko will meet while attending the Asia-Europe Meeting summit in Milan, Poroshenko said on a visit to Kharkiv.

"I don't expect that these will be easy negotiations," he said, adding that the talks will also include the prime ministers of Italy and the United Kingdom, as well as German Chancellor Angela Merkel.

Poroshenko said he will discuss with Putin the peace plan and cease-fire, and "the issue of controlling the fulfillment of the agreement", as well the gas dispute with Moscow that threatens to plunge Ukraine into a very cold winter.

"We are very close to regulating the issue of the gas dispute with Russia right now," he said. "I hope that there will be considerable progress" on that.

Putin and Poroshenko last met one-on-one in late August in the Belarusian capital of Minsk, after which Kiev announced a truce accord with rebels.

Newly appointed Donetsk Governor Oleksandr Kykhtenko also said the meeting will address the threat of the region's population being cut off from Kiev's support ahead of a cold winter.

Two more civilians were killed on Saturday when a shell landed on their building, authorities in Donetsk said, adding to three deaths a day earlier.