Fighting for control of a key army base in Aleppo raged on Saturday, as Russia tried to revive a divisive accord on ending the bloodshed that calls for a government of unity in Syria.
As Lakhdar Brahimi prepared for his first visit to Damascus as international envoy on Syria, EU foreign ministers meeting in Cyprus upped the pressure, saying they agreed on the need to beef up sanctions against the Syrian regime.
On the ground, the army claimed a victory against rebels in the northern city of Aleppo, ousting them from the Hanano army base backed by armour and helicopters in a 20-hour battle, military sources and witnesses said.
"There are a lot of victims on both sides," one witness told AFP.
A military official said soldiers destroyed six armoured vehicles the rebels were using to transport arms seized from the barracks that serves mainly as a weapons depot and recruitment centre.
Rebels on Friday claimed to have captured parts of the barracks.
"The rebels had thrown themselves whole-heartedly into this offensive because they desperately need weapons," an army official said.
Badly outgunned members of the Free Syrian Army (FSA) took part in the offensive, a rebel commander calling himself as Abu Omar said on Friday.
The goal was to liberate Hanano, cut off supply lines and stop shelling that has caused many civilian casualties in Aleppo.
Later, it was reported that a main water line had been destroyed, with Rami Abdel Rahman, director of the Syrian Observatory for Human Rights, saying this was critical "because it provides drinking water to the whole city."
"We cannot say how it was ruptured, but there were air strikes and clashes between the army and rebels in the area," he added.
Aleppo provincial governor Mohammed Wahid Akkad blamed a "terrorist" attack and said work was under way to restore supplies, the official SANA news agency reported.
The Local Coordination Committees, a network of opposition activists on the ground, blamed the damage on regime air attacks.
The rebels also assaulted Aleppo's Midan district by breaking into the Saint Vartan religious complex between the central district and a rebel stronghold, a military source and local residents said.
They tried to take Midan "but were met with fierce resistance by the security forces of the air force, who are in charge of the area," the source added.
The Observatory also reported shelling in Damascus, in the southern province of Daraa, and clashes around a military airport in Albu Kamal in the east.
The fighting also spilled over into Iraq, when mortar rounds hit the border town of Al-Qaim, killing a four-year old girl and wounding four people, an Iraqi army captain said.
At least 80 people -- 25 civilians, 19 rebels and 36 soldiers -- were killed nationwide on Saturday, the Observatory reported, following a day in which 136 people died.
On the political front, Russia said it would ask the UN Security Council to endorse a plan to end the violence in Syria, but the United States insisted any resolution had to have teeth.
Moscow has been the main diplomatic and military supporter of Syria's embattled President Bashar al-Assad and has angered Western nations by vetoing, along with China, three Security Council attempts to exert more pressure.
"There is a plan to hold a special meeting of the UN Security Council with the participation of ministers on the Syrian issue," Foreign Minister Sergei Lavrov said after meeting US Secretary of State Hillary Clinton in Vladivostok.
"We stressed in a meeting with the US Secretary of State that Russia will push for the Security Council's approval of the Geneva communique."
Clinton said she was open to another attempt at the Security Council based on the Geneva plan, but insisted on a resolution to carry consequences if Assad did not comply, a senior US official said.
On June 30, world powers agreed on a plan calling for all sides in Syria to implement a ceasefire and then form a transitional government and review the constitution.
But the plan did not make an explicit call for Assad to quit -- a demand championed by the United States, Britain, France and Arab states including Saudi Arabia and Qatar who have also been clamouring for tougher sanctions on Syria.
Cypriot Foreign Minister Erato Kozakou-Marcoullis said there was "consensus" in informal talks in Cyprus on Saturday among EU foreign ministers on increasing sanctions against Syria.
Spain's Foreign Minister Jose Manuel Garcia Margallo said "there is a general feeling that more pressure must be placed on the regime" to end the violence and enable the distribution of humanitarian aid.
In that vein, German Foreign Minister Guido Westerwelle visited a refugee camp in neighbouring Jordan, and said "it's absolutely necessary that the international community help Jordan manage this complicated situation."
He also insisted that Assad be further isolated, saying Germany would use its coming weeks as Security Council president to work to that end.
"We think that he will fall; we think his time is over and that these atrocities are in no way acceptable, so we think it's necessary we stand united as an international community."
He added that Syria's opposition should unite and "work out a common platform for democracy and a new Syria with rule of law."
Brahimi, who heads to Cairo for talks with Arab League leaders on Sunday before finalising a visit to Damascus, has said it is up to the Syrians to decide their future, echoing the position of his predecessor Kofi Annan.