Residents of the Syrian capital were facing their third consecutive day of water shortages on Sunday, with authorities accusing "terrorist groups" of deliberately poisoning water resources.

The government cut off water to Damascus on Friday after concerns that rebel groups west of the city had poisoned wells and pipes.

A statement by the Damascus City Water Supply and Sewage Authority said it had halted supplies after "terrorist attacks on all water resources feeding into Damascus and its surroundings".

It said it was using reserves and would pump water to various city neighbourhoods according to a schedule published on its website.

"Water has been totally cut for three days," said Rasha, a 51-year-old housewife.

"We can live without electricity but we can't live without water."

Supplies were pumped briefly to two districts on Saturday, AFP correspondents said, but tanks were empty again on Sunday.

According to state news agency SANA, rebel groups attacked springs at Wadi Barada and Ain al-Fijeh, about 15 kilometres (9 miles) northwest of Damascus.

It did not specify the type of attack, but the daily Al-Watan, which is close to the government, accused rebels of "contaminating the water resources into Damascus with pollutants and diesel".

An estimated 1.5 million people live inside Damascus city, with another 3.5 million in its suburbs.

While the capital has remained relatively insulated from the country's brutal internecine war, rebel factions have seized territory across Damascus province.

The water shortages have come as Syrian government forces bombard Wadi Barada and Ain al-Fijeh, the Syrian Observatory for Human Rights said.

The Britain-based monitor said regime forces were shelling the area "to put pressure on Islamist rebel factions and Fateh al-Sham Front to accept a reconciliation deal".

Fateh al-Sham, formerly Al-Nusra Front, changed its name after renouncing ties to Al-Qaeda.

Under such local reconciliation deals, rebels agree to leave a town or village in exchange for safe passage elsewhere, often after months of devastating siege or bombardment.

Over the past five months alone, such agreements have seen at least six towns around Damascus evacuated, with rebels, their families and other civilians bused to other opposition-held areas in northern Syria.

More than 310,000 people have been killed since Syria's conflict erupted nearly six years ago.