Near a church in old Damascus, people in a long queue wait impatiently for the tanker to fill their canisters after being deprived of water for a week.

"I can't carry more than one can, (but) my sons are coming soon with a jerrycan each and we'll have enough water for two or three days," says Abu Assaad Hawasli, wearing a thick woollen sweater.

The water shortage in Damascus is the result of fighting between the regime and rebels in the region of Wadi Barada, northwest of the Syrian capital and its main source of water.

The two sides accuse each other of responsiblity for the shortages.

And despite a nationwide ceasefire that began at midnight after an agreement brokered by Turkey and Russia, clashes erupted in the Wadi Barada region on Friday.

"It's been an hour and I'm still waiting," says Hawasli, a man in his fifties.

From his shop, Essal Dalati watches those queueing for water.

"The truck came two days ago and I took 20 cans that I have kept for my family," he says.

"Difficult days await us. Nothing can replace water."

- Millions without water -

Taps are dry for all but one or two hours every three days, says an AFP correspondent in Damascus.

To compensate for the crisis, tanker trucks distribute water from the capital's reserves, alternating in different districts.

Four million people in Damascus and its suburbs have now been without water since December 22, according to the UN Office for the Coordination of Humanitarian Affairs, or OCHA.

"Two primary sources of drinking water -- Wadi Barada and Ain al-Fijeh -- which provide clean and safe water for 70 percent of the population in and around Damascus are not functioning, due to deliberate targeting resulting in the damaged infrastructure," OCHA said in a statement.

The regime launched an offensive last week against rebel-held areas in Wadi Barada.

Infrastructure at the pumping station has been damaged, but the regime and the insurgents deny responsibility.

- 'Contaminated' water -

"Armed groups contaminated the source at Ain al-Fijeh with diesel and large quantities have spread to Wadi Barada," said a military source.

The rebel fighters then "completely cut off the water from Damascus to put pressure on the army and get the military operations to stop," the source told AFP.

The shortage of water is likely to continue in Damascus.

Even after an army victory, it would take the authorities around 10 days to "repair the damage caused to the Ain al-Fijeh station", said a government official.

As a result of the crisis, Abu Hassan is overwhelmed by the number of customers at his shop in Mazza on the outskirts of Damascus.

Since they are unable to wash their dishes, dozens of men and women come to the business to buy disposable plates and cutlery.

"In two days, we sold more than we did in a month," says Abu Hassan, whose phone rings constantly.

"I've exhausted all my plastic glasses, but I'm unhappy to see the sadness in people's eyes."

One of his customers, Hawraa, 28, checks her shopping list as she waits to be served.

"It's been a week since I had any water at home," she says. "I have to wait to go to work to go to the toilet."

But even that is a luxury for another client, Abdallah Rai.

Upon arriving at his workplace in central Damascus, a sign was displayed on the toilet door: "Out of service".