Syrian government forces have recaptured all towns and villages in the Wadi Barada valley near the capital, Damascus, according to a statement by the Syrian military.

"Units of our armed forces, together with ... allied forces have achieved their mission in returning security and stability" to the area, said the statement, read out by a military spokesman on Syrian state TV on Sunday.

The Syrian army and its allies took over a Wadi Barada village containing a major spring and pumping station that supplies most of Damascus' water on Saturday.

Heavy clashes between government troops and rebel forces were sporadic in Wadi Barada since a December 30 ceasefire brokered by Russia and Turkey.

Fighting continued even after a negotiated deal to restore water to Damascus earlier this month.

Under the agreement, teams were meant to repair the infrastructure that supplies Damascus with water in exchange for a cessation of hostilities and the withdrawal of rebel fighters willing to do so.

About 5.5 million in Damascus and its suburbs have been without water since December 22.

The Syrian conflict started as an uprising against President Bashar al-Assad in March 2011. It subsequently escalated into a full-scale civil war that has left hundreds of thousands of people dead and more than half the country's pre-war population displaced.

OPINION: Astana - What talks?

United Nations-hosted negotiations on the Syrian conflict planned for February 8 in Geneva have been postponed until the end of that month, Russian Foreign Minister Sergey Lavrov said last week.

"The date of February 8 has been put back until the end of next month," Lavrov said at a meeting on Friday with Syrian opposition groups in Astana, Kazakhstan, that ended last week without a major breakthrough.

Key players Russia, Turkey and Iran backed the Astana talks, also attended by government representatives, and the main result was an agreement by the three sides to try to shore up a shaky ceasefire on the ground in the war-torn country.

The latest peace initiative to halt fighting comes after the Syrian army, backed by Russian and Iranian firepower, dealt rebels a crushing blow by forcing them out of eastern Aleppo last month.