Russia's military on Wednesday said it had set up a zone north of the Syrian city of Aleppo to stop clashes between Kurdish fighters and opposition rebels.

"To prevent provocations and possible clashes between the Free Syrian Army in northern Syria and Kurdish militia, a de-confliction zone was created in Tal Rifaat district," senior Russian military officer Sergei Rudskoi told a briefing.

"Contingents of Syrian government forces have replaced Kurdish armed groups which have left this district" and "a contingent of Russian military police has been brought in to the area" and set up checkpoints, Rudskoi said.

The Kurdish People's Protection Units (YPG) last month said that under an agreement with Moscow, "Russian military observers" would "deploy along multiple points" in the area to monitor and provide security.

Rudskoi said about 400 people have returned to their homes in Tal Rifaat since the de-confliction zone was established.

Speaking the day after Syrian government forces broke the blockade of the Islamic State group of their stronghold Deir Ezzor, Rudskoi further said that the Syrian army had "achieved serious success" in east and central Syria over the past two weeks.

He said it had freed 59 towns and villages from "terrorists."

It was not clear whether he was referring to the so-called Islamic State (IS) group or other organisations that the Syrian government has been fighting in the complex, years-long conflict.

"The average speed of the advance by the government troops over the last three days was 15-20 kilometres (nine to 12 miles) a day," the commander of Russian forces in Syria, Sergei Surovikin, said at the briefing.

"The operation to liquidate the last major base of the terrorists in Syria is being completed," he said.

Russian warplanes carried out 2,687 strikes in support of the offensive over the past two weeks, he said.