AMMAN: Rebel forces fought to drive back a regime advance 15km northwest of Damascus on Sunday, one day after the collapse of a short-lived agreement to resolve the capital city’s month-long water crisis and the assassination of the lead mediator who was respected by both sides, local sources told Syria Direct.

The breakdown in negotiations comes amidst the first regime advances in a 25-day campaign to wrest control of the capital’s largest freshwater source from opposition hands.

On Saturday, regime forces and allied Hezbollah fighters broke through the opposition’s frontlines for the first time in Wadi Barada, a constellation of 13 villages that supplied Damascus with 70 percent of its water before the destruction of the area’s primary water-pumping station last month. Dozens of airstrikes, barrel bombs and heavy artillery fire paved the way for the regime’s capture of the village of Baseema, located in the southeast of the opposition pocket.

Late Saturday evening, any hope of a tenable ceasefire collapsed after the assassination of Ahmed al-Ghadban, the retired major general of the Syrian Arab Army and lifelong resident of Wadi Barada who served as the mutually respected negotiator between rebel and regime forces within the disputed pocket. The circumstances of al-Ghadban's death remain unclear.

Within opposition circles, Syria’s rebels claim Hezbollah orchestrated the assassination. The attack came from “a Hezbollah sniper” at a checkpoint near Deir Qanun, Abu Mohammad al-Baradawi, a spokesman for the Wadi Barada Media Center, told Syria Direct on Monday.

“His loss in indescribable,” al-Baradawi added. “He wasn’t just a member of the negotiating committee, he was a son of Ein al-Fijeh. He was the biggest personality in all of Wadi Barada.”

Meanwhile, pro-regime media was swift to claim that “terrorists,” an all-encompassing term often used to describe Syria’s armed opposition, carried out the attack.

While opposition media reports that the attack occurred in the Wadi Barada village of Deir Qanun, SANA, Syria’s state media outlet, reported on Saturday that “terrorists shot al-Ghadban” at a different location, five kilometers northeast, after he left a meeting “with leaders of armed groups in the Ein al-Fijeh village.”

On Friday, al-Ghadban reached a political solution between the two parties. The Friday agreement ushered in an immediate ceasefire, permitted regime repair teams to restore operation to the Ein al-Fijeh water pumping station and outlined the terms of a rebel surrender of Wadi Barada, according to a copy of the terms obtained by Syria Direct.

The agreement—heralded by both rebels and the regime as a political victory—quickly unraveled within hours of the assassination, with multiple reports of shelling and gunfire targeted the regime repair teams. Regime and rebel media traded accusations regarding the attacks.

Despite the Governor of Outer Damascus Ala’a Ibrahim reportedly telling reporters in Deir Qanun on Friday that water service would return to Damascus “within three days,” the regime’s repair teams were unable to fix the Ein al-Fijeh pumping station over the weekend.

While the intermittent attacks caused tension on the nascent ceasefire, the assassination of al-Ghadban led opposition media to call the agreement “suspended.”

“The regime never abided by the truce,” al-Baradawi of the Wadi Barada Media Center told Syria Direct. “On the contrary, they exploited the ceasefire to make surprise attacks—truly vicious attacks—on Baseema, which is what ultimately allowed the regime to capture it after they had been unable to do so for so long.”

Al-Baradawi calls the regime’s assault on Baseema a “scorched earth offensive,” claiming that pro-Assad forces not only captured the village, “they looted Baseema and then burned it to the ground.”

Reeling rebel forces are on the defensive on Sunday, as pro-Assad loyalists attempt to capitalize on their weekend gains and recapture additional territory from the Wadi Barada pocket, which the opposition has held since 2012.

 Regime shelling hits Wadi Barada on Thursday. Photo courtesy of the Wadi Barada Media Center.

Regime forces reportedly made advances in the direction of Deir Miqrin, al-Baradawi added, in a strategy aimed at pinching Ein al-Fijeh between two flanking advances.

On Sunday, regime forces “perpetrated a massacre” in Wadi Barada, killing 12 civilians and injuring 20 more, some in serious condition, after a tank fired on civilians near Deir Qanun, opposition media reported. Syria Direct could not immediately confirm the details of the incident.

Inside Wadi Barada, “there’s a sense of immense concern,” Abu Omar Mohammad, a local activist, told Syria Direct on Sunday.

“People are tremendously sad after the death of Ahmed al-Ghadban and just as worried for the failure of the ceasefire,” he added. “People are scared of the escalation that is to come, especially after al-Ghadban’s death.”

Sunday’s clashes come one week after Syrian President Bashar al-Assad was quoted as saying that that the region of Wadi Barada is exempt from a nation-wide ceasefire signed in Ankara on December 30.

“The terrorists occupy the main source of water of Damascus…and the role of the Syrian army is to liberate that area in order to prevent those terrorists from using that water in order to suffocate the capital,” Assad told members of the French media, assembled in Damascus.

As a result of the nearly month-long fighting in Wadi Barada, up to 5.5 million residents across Syria’s capital and adjacent suburbs are grappling with wide-scale water shortages.

Pro-regime sources say water stopped pumping to the capital on December 22 after rebels contaminated the area’s Ein al-Fijeh spring with diesel. Rebels deny the accusation, blaming government bombings for destroying Wadi Barada’s water-pumping station.

Among Syrians, Wadi Barada is best known as the home of Ein al-Fijeh, which provides drinking water to many of the capital’s neighborhoods, including Mezzeh and Malki, the wealthiest districts that count top regime officials and supporters among its population.