Syrian forces backed by helicopter gunships and tanks launched a deadly assault on parts of Damascus Wednesday, activists said, as the regime battles to stamp out rebel resistance in the capital.
At least 37 people were reported killed in Damascus alone, a day after a top minister hinted that the embattled regime was ready to discuss President Bashar al-Assad's exit in any talks on ending the brutal 17-month conflict.
Fighter jets and artillery hit the commercial capital Aleppo and heavy shelling was reported in Daraa, the birthplace of the uprising, and the eastern town of Deir Ezzor while rebels claimed they seized parts of a town on the Iraq border, a watchdog said.
The army attacked several areas where anti-regime sentiment is strong in and around the southwest of Damascus, including with heavy shelling, helicopter fire and mass arrest sweeps, the Syrian Observatory for Human Rights said.
In the deadliest operation, the army raided the southwestern district of Kafr Sousa, killing at least 24 civilians, it said, while a pro-opposition journalist was also killed during a raid on his home in Damascus.
The violence was some of the worst since regime forces reclaimed most of the capital a month ago, and dozens of bullet-riddled bodies were found in the Damascus suburb of Qaboon, according to the Observatory.
Meanwhile the opposition Syrian National Council urged the UN to investigate reports that dozens of people were killed during shelling and in summary executions in Maadamiyat al-Sham, a town west of Damascus.
The SNC described what happened as a "brutal crime" and urged the Arab League to hold an emergency meeting to discuss "war crimes" perpetrated by the regime in Syria."
The state-run news agency SANA, meanwhile, quoted an official source as saying that troops clashed with an "armed terrorist group" in Daraya, a suburb just south of Damascus, and seized weapons and a bomb-making factory.
It also reported that the army "inflicted heavy losses on terrorists" in Aleppo.
At least 115 people including 71 civilians were killed nationwide on Wednesday, according to the Observatory, which says a more than 23,000 people have died since the uprising began in March 2011.
Among the latest casualties, four Lebanese villagers died in an air strike while fighting alongside the rebels, according to a security source in Lebanon.
The Observatory has a network of activists on the ground but its claims cannot be independently verified.
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As the fighting raged, British Prime Minster David Cameron and US President Barack Obama warned they would be forced to consider a new course of action if Syria threatened to use chemical weapons against rebel fighters.
The two leaders agreed during a telephone call, details of which were later released by Cameron's Downing Street office, that the use of chemical weapons would be "completely unacceptable".
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"Both said that they wanted to see a credible opposition and hoped that the opposition would use their upcoming meeting in Cairo to show real unity of purpose and coherence in working towards transition," added the statement.
Cameron spoke separately to French President Francois Hollande in a bid to ensure that Syria remained the focus of international attention.
The United States and France again pushed for Assad to resign after a top Syrian official said on Tuesday that Damascus was ready to discuss his exit as part of a negotiated settlement to the conflict.
"As far as his resignation goes -- making the resignation itself a condition for holding dialogue means that you will never be able to reach this dialogue," Deputy Prime Minister Qadri Jamil said in Moscow.
But he added: "Any problems can be discussed during negotiations. We are even ready to discuss this issue."
Moscow, however, bluntly told the West not to meddle in Syria after Obama hinted at possible military action if Damascus resorted to its chemical weapons arsenal.
"There should be no interference from the outside," Foreign Minister Sergei Lavrov said after talks with Jamil. "The only thing that foreign players should do is create conditions for the start of dialogue."
Washington was unimpressed by the apparent overture from Damascus.
"We still believe that the faster Assad goes, the more chance there is to quickly move on to the day after," US State Department spokeswoman Victoria Nuland said, dismissing Jamil's comments as "nothing terribly new".
US Defense Secretary Leon Panetta said that the United States was preparing for "threats" from Iran and Syria's turmoil as an aircraft carrier headed to the region ahead of schedule.
The USS John Stennis and its strike group will set forth shortly for the Middle East, a deployment ordered four months ahead of time to minimize the gap in which the United States has only one carrier in the region.
In Aleppo, fighter jets struck near a missile depot, and shelled several other areas of the city that has become the key battleground since fighting first erupted there a month ago, the Observatory said.
It also said rebel fighters had seized an intelligence office and checkpoints in the eastern town of Albu Kamal on the Iraqi border, although regime forces remained largely in control.
Lashing out primarily at regime troops for launching indiscriminate attacks, Amnesty International meanwhile said Syrian civilians were facing "horrific" violence as the battle for Aleppo rages.
"The use of imprecise weapons, such as unguided bombs, artillery shells and mortars by government forces has dramatically increased the danger for civilians," Donatella Rovera, Amnesty International Senior Crisis Response Adviser, who recently returned from Aleppo, said in a statement.
The conflict has spilled over again into neighbouring Lebanon, with nine dead in clashes that first erupted late Monday between pro- and anti-Damascus regime supporters in the northern port city of Tripoli.
The United Nations puts the death toll at 17,000 and says hundreds of thousands more have fled to Syria's neighbours while another 2.5 million still in the country are in desperate need of aid.