Turkish foreign minister warns planned peace talks in Kazakhstan could fail if violations do not end.
Turkey has accused the Syrian government of violating a fragile ceasefire in the country and said the new round of negotiations to be held in Kazakh capital Astana was at risk.
The Russian-Turkish brokered ceasefire last week has brought calm to large parts of Syria, but has been threatened by ongoing fighting in the Wadi Barada region near the capital Damascus.
Turkish Foreign Minister Mevlut Cavusoglu on Wednesday urged the Syrian government and its backers to end their "violations" of the truce, warning they were jeopardising the planned talks to be held in Astana this month.
"If we do not stop the increasing violations, the Astana process could fail. After the ceasefire, we see violations," Cavusoglu told the state-run Anadolu news agency.
Syrian government forces backed by Lebanon's armed Hezbollah group are fighting to recapture Wadi Barada, the main source of water to Damascus.
Cavusoglu urged Russia and Iran, which both back Syrian President Bashar al-Assad and are also helping prepare the Astana talks, to pressure Damascus and Hezbollah to stop the fighting.
Despite the call, fighting continued on the ground in Wadi Barada on Wednesday, the UK-based Syrian Observatory for Human Rights, a monitoring group, said.
It reported ongoing clashes as well as government air strikes and artillery fire in the area, but had no immediate details on casualties.
Syria's main rebel groups said on Tuesday they have already frozen their participation in the preliminary peace talks due to what they called several "violations" by the regime of the truce that came into effect last week.
"The regime and its allies have not stopped shooting and have launched major and frequent violations, notably in the regions of Wadi Barada and Eastern Ghouta," the groups said in a joint statement.
Water supply damaged
Wadi Barada has been under government siege since 2015, but government forces upped the pressure on the region several weeks ago as they tried to secure a "reconciliation deal" with rebels there.
The regime has reached a series of such deals with opposition forces around Damascus in recent months, offering rebels safe passage to other parts of the country in return for their surrender.
The government accuses rebels in the area of deliberately targeting water infrastructure, causing leaking fuel to poison the supply to the capital, and then cutting the flow altogether.
Rebels say the infrastructure was damaged in government strikes, and deny responsibility for the damage that has left four million people without water since December 22.
The UK-based Observatory said about 1,000 civilians - all of them women and children - fled the fighting in Wadi Barada over the weekend, moving to other parts of the province.
Syria's conflict started as a largely unarmed uprising against Assad's rule but quickly turned into a full-scale civil war that has killed at least 400,000 civilians, according to United Nations estimates.