A boy rides a bicycle past damaged buildings in the rebel held besieged city of Douma, in the eastern Damascus suburb of Ghouta, Syria January 8, 2017. [Photo/Agencies]

Assad blamed truce violations on the insurgents, and said the army must "prevent terrorists from using the water to throttle the capital". He said it was the army's job to recapture the Wadi Barada area, which he said had been occupied by a jihadist group not covered by the ceasefire.

Rebels deny the area is in jihadist hands.

The United Nations has said 5.5 million people have had little or no running water for more than two weeks in Damascus. It blamed "deliberate targeting" for destroying the pumping station, without saying by whom. Rebels accuse the government.

Talks between the government and rebels aimed at allowing repairs to the pumping station failed at the weekend, and heavy air strikes were reported in the area on Sunday.

The Syrian Observatory for Human Rights, a Britain-based war monitor, reported clashes in Wadi Barada on Monday and said government forces shelled several towns there.

In Idlib province in the north, a military media unit run by Damascus's ally Hezbollah said rebel shelling killed two people in the pro-government villages of al-Foua and Kefraya.