The United Nations mediator on Syria said moribund peace talks on the conflict could be resumed if a faltering truce was extended to the city of Aleppo, something he and the Russian foreign minister said might happen within hours. An escalation of violence in the divided northern city has undermined efforts to end the Syria crisis. Staffan de Mistura, the U.N. envoy, made his upbeat comments on Tuesday after holding talks with Russian Foreign Minister Sergei Lavrov in Moscow, saying he thought there was now a chance to relaunch the cessation of hostilities by reinforcing and extending local truces. "I have a feeling and a hope that we can relaunch this," De Mistura told a news conference after the talks. "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." His meeting in Russia came after U.S. Secretary of State John Kerry spoke via telephone with his Russian counterpart Sergey Lavrov about ways to restore a fresh cease-fire throughout Syria, the State Department said."Both ministers, again talked predominantly about the cessation, acknowledging that it is in fact fragile and, talking about ways in which it can be restored throughout the country quite frankly," according to agency spokesman John Kirby. The U.S. and Russia agreed Friday to reinforce a short-term cease-fire for some cities in Syria, where attacks against civilians have increased recently. "Over the weekend, we did see in areas around Latakia and in areas around Damascus, we did see a restoration of the cessation of hostilities," Kirby said. "We have always been focused on areas like Aleppo, and that was certainly a topic of the discussions that the secretary had in Geneva and with Foreign Minister Lavrov today." British Foreign Secretary Philip Hammond said on Monday he was deeply concerned about the state of the ceasefire in Syria and that a new initiative was needed to keep dialogue alive. "There is a need for a new initiative in the Syria dialogue to keep it alive, the Syrian moderate opposition is finding it increasingly difficult to justify their participation in a political process," Hammond told reporters during a visit to Mexico City.In Aleppo the clashes between the regime forces and the opposition groups continued. Syrian opposition fighters on Tuesday shelled government-held parts of Aleppo, killing at least 12 people, as the army claimed it was repelling a wide offensive by the rebels in the country's largest city. Activists, meanwhile, said government forces were also shelling rebel-held parts of the city, killing two people and wounding several. Syrian state TV said shells hit a government-held area during morning rush hour, killing seven people and wounding at least 35, while activists reported two dead in a rebel neighborhood. Hours later, some rockets hit a hospital killing and wounding dozens of people, the TV said. The TV said one of the rockets hit the Dubeet hospital in the central neighborhood of Muhafaza. The TV did not give a breakdown of the casualties. "Shells and mortar rounds are raining down on every neighborhood Aleppo," said Aleppo-based health official Mohammad Hazouri, speaking from Al-Razi hospital. He said four people were killed and more than 30 wounded in Dubeet hospital alone, adding that half the casualties at the hospital were women and children. He said the rebel bombardment of government-held parts of Aleppo on Tuesday killed a total of 12 people and wounded more than 70. The Lebanon-based Al Mayadeen TV that has reporters in the government-held parts of Aleppo showed damage on both sides of the street in front of the hospital, which also appeared heavily damaged. Cars in the street were scorched and some were turned over. The shops on the other side of the street showed moderate damage as smoke still climbed out of the wreckage.Also in northern Syria, warplanes carried out intense airstrikes on the city of Raqqa, the de facto capital of the extremist DAESH, in the early hours Tuesday. Activist groups said it was not clear if the warplanes were Russian or those of the U.S.-led coalition. The Observatory, which has a network of activists around the country, said there were more than 35 air raids and that 18 people were killed, including five members of DAESH. It said dozens were wounded. The anti-DAESH group Raqqa is being Slaughtered Silently said the airstrikes killed 10 and wounded dozens, but different casualty figures are common in the chaos of Syria's civil war. The group said there were calls from mosque loudspeakers for the residents to donate blood.Meanwhile, fighting erupted east of Damascus on overnight Tuesday despite a temporary truce announced by the Syrian army in that area, a war monitor said, and rebel group Jaish al-Islam said it had lost ground to the government there. Local ceasefires were announced late last week in the Eastern Ghouta area near Damascus and in northern areas of Latakia province. Washington and Moscow said on Monday they were working hard to extend the truce to Aleppo. An opposition activist in northern Latakia told Reuters the area had been completely calm for three days.