Beirut/Moscow: Rebel fighters launched an assault in Syria's divided northern city of Aleppo on Tuesday and fired rockets on a hospital, in the latest violence to hit civilians as diplomats struggled to restore an unravelling ceasefire and resurrect peace talks.
The Syrian Observatory for Human Rights, a British-based group that monitors the conflict, said rebel rockets had killed 19 people in government-held territory, including an unspecified number at the Al Dabit hospital.
It described a rebel offensive that led to casualties on both sides. Rebels had hit a government gun position with a guided missile.
The Syrian state-run Ikhbariya news channel said three women were killed at the hospital and 17 people wounded. A Damascus Information Ministry statement called it a crime against humanity.
The rebel attack followed government air strikes on rebel areas, including one that hit a hospital last week, which medical charity Medecins Sans Frontieres said killed 55 civilians.
Aleppo has been the scene of the worst surge in fighting in recent days, wrecking the first major ceasefire of the five-year-old civil war, sponsored by the United States and Russia, which had held since February.
In an effort to revive the ceasefire, temporary local truces have been put in place in two parts of Syria, but those have not been extended to Aleppo, Syria's largest city before the war and its biggest strategic prize now.
UN Syria envoy Staffan de Mistura, who met US Secretary of State John Kerry in Geneva on Monday and Russian Foreign Minister Sergei Lavrov in Moscow on Tuesday, said he hoped the truce could be extended to Aleppo swiftly.
"We all hope that ... in a few hours we can relaunch the cessation of hostilities. If we can do this, we will be back on the right track," de Mistura said. If the truce were extended to Aleppo, peace talks could resume, he said.
Lavrov said: "The process of agreeing a ceasefire in Aleppo is being finished right now between Russian and American military personnel."
He added that he hoped it could be announced in the near future, "maybe even in the coming hours".
The Aleppo fighting threatens to wreck the first peace talks involving the warring parties, which are due to resume at an unspecified date after breaking up in April when the opposition delegation walked out.
Washington and Moscow, co-sponsors of the ceasefire and peace talks, have announced a new joint centre in Geneva to monitor the ceasefire, to be staffed around the clock by US and Russian officers.
The two governments have been working to extend the local truces to Aleppo but so far have not been able to do so, although both have expressed optimism that this can be achieved.
The Observatory has reported 279 civilians killed on both sides in Aleppo since April 22, by intense government air strikes and rebel shelling, with 155 killed in opposition-held areas and 124 in government-held districts.
Tuesday's rebel ground assault focused on the Jamiat Al Zahraa area of the city, where insurgent groups took a few buildings before advances were checked by the arrival of reinforcements on the government side, the Observatory said.
A Syrian army source said a car bomb was used in an attack nearby, but the assault had failed. "Matters had been moving towards Aleppo being included in the truce, but it seems there are those who do not want that," the source said.
A Syrian army statement on Tuesday said the rebel attack on the hospital came "at a time when international and local efforts are being made to shore up" the ceasefire and extend the truce to Aleppo.
In a statement, the Nour Al Edin Al Zenkey rebel group accused the government of launching the first ground assault on Tuesday, saying it had attacked west of Aleppo. The group said the assault was successfully repelled and was followed by a counterattack in which rebels captured several positions.
Kerry said on Monday he hoped for more clarity in the next day or so on restoring the nationwide ceasefire.
The United States and Russia have taken the leading roles in diplomacy since Moscow joined the war last year with an air campaign that tipped the balance of power in favour of President Bashar Al Assad, its ally.
Washington is among Western and regional powers that say Assad must leave office. The White House said on Monday Assad's government needed to live up to its ceasefire commitments.
The civil war in Syria has killed hundred of thousands of people, driven millions from their homes, created the world's worst refugee crisis and provided a base for IS militants who have launched attacks elsewhere.
All diplomatic efforts to resolve it have foundered over the fate of Assad, who refuses to accept opposition demands that he leave power.
Aleppo remains the biggest prize for Assad's forces hoping to take full control of the city. The nearby countryside includes the last strip of the Syria-Turkish border in the hands of rebels.
The opposition accuses the government of deliberately targeting civilians in rebel-held parts of Aleppo to drive them out. For its part, the government says rebels have been heavily shelling government-held areas, proving they are receiving sophisticated weapons from foreign sponsors.