BEIRUT — Damascus and Aleppo came under shell fire on Thursday as troops loyal to President Bashar al-Assad stepped up efforts to crush rebels threatening the government's two main power centers.
One of the most senior figures to defect from Assad's inner circle, Brigadier General Manaf Tlas, put himself forward as someone who could help unite the fragmented opposition inside and outside Syria on a plan for a transfer of power.
Turkey laid down a marker by threatening to act against "terrorists" in northern Syria, a reference to Kurdish militants linked with the Kurdistan People's Party (PKK).
Turkish Prime Minister Tayyip Erdogan said he would strike against Kurdish militants in Syria if need be, mirroring Ankara's policy of attacking PKK bases in northern Iraq used for the group's long-running armed struggle in southeast Turkey.
Turkey, a former friend of Assad and now one of his severest critics, closed its border posts with Syria on Wednesday to all traffic except Syrian refugees.
A bomb attack that killed four of Assad's closest lieutenants in Damascus last week and the surge of fighting there and in Aleppo prompted predictions among the 46-year-old president's enemies that his time in power was nearly over.
Assad himself has not spoken in public since the 18 July bombing, although he has appeared at formal televised events.
Shelling in Damascus
Nevertheless, his forces have hit back hard, driving rebels out of most of Damascus, where opposition sources report executions of insurgents, and then counter-attacking in Aleppo, using helicopter gunships backed by combat aircraft.
Residents in the capital reported a shell landing in southern districts every minute on Thursday morning. Helicopters attacked Hajar al-Aswad, one of the last rebel-held districts in the city after days of street fighting, activists said.
Rebels said they had destroyed two Syrian army tanks.
"The Assad forces are trying to storm Hajar al-Aswad from more than one front. The (rebel) Furqan Brigade is engaging with them. There is a fierce battle," activist Mansour Abdallah said.
Rocket fire killed 16 people, including women and children, during an army offensive in the southern Damascus district of Yalda on Thursday, according to the Syrian Observatory for Human Rights, which monitors violence in Syria.
The Observatory also said the bodies of 12 rebels were found in the Ajami area near the Jordanian border, in the south of the country. It said they were killed in shelling on Wednesday.
The army has sent reinforcements to Aleppo, determined to keep control of Syria's biggest city and commercial capital.
Fierce clashes raged there overnight, and one activist said rebels now controlled half the city, a claim that could not be independently verified, like others made by both sides.
"There was shelling this morning on the Salaheddine and Mashhad districts," said Aleppo activist Abu Hisham. "Now it has stopped, but helicopters are buzzing overhead."
According to the opposition Syrian Observatory for Human Rights, the army also shelled three districts in the central city of Homs, scene of some of the worst violence of a revolt in which dissidents say more than 18,000 people have been killed.
Raising the alarm over Aleppo, French Foreign Minister Laurent Fabius urged Russia and China to act with the United Nations Security Council to prevent a "bloodbath".
UN Secretary-General Ban Ki-moon warned world powers not to repeat in Syria the mistakes they made in Bosnia, during a visit to Srebrenica where UN peacekeepers failed to prevent the massacre of 8,000 Muslim men and boys in 1995.
"I don't want to see any of my successors after 20 years visiting Syria and apologizing for what we could have done now to protect civilians in Syria, which we are not doing," he said.
Transition role
General Tlas, a former friend of Assad's who some have suggested could play a part in any transition of power, said he had not defected from Syria to seek a leadership role.
"I am discussing with … people outside Syria to reach a consensus with those inside," he told the Saudi newspaper Asharq al-Awsat in an interview published on Thursday.
"I left (Syria)…to try to help the best I can to unite the honorable people inside and outside Syria to set out a road map to get Syria out of this crisis".
Tlas, a former Republican Guard commander and a symbol of a now-fractured alliance between Assad's Alawite-dominated system and elements of the Sunni Muslim majority, defected this month and is now in Jeddah, apparently enjoying Saudi support.
Russia, one of Assad's few remaining allies, said calls for Assad to quit power were blocking efforts to end the conflict.
Foreign Minister Sergei Lavrov said such calls, led by the United States, Turkey and other Western and Arab nations, were fanning violence. He reiterated Moscow's contention that support for Syrian rebel groups was tantamount to backing terrorism.
"We propose things that would allow for an immediate ceasefire, but the other side says, 'No, either the regime capitulates or we will continue to back … the opposition's armed fight', justifying terrorist acts," Lavrov said.
Russia and China have been bitterly criticized by Western states for three times vetoing UN Security Council resolutions intended to push Assad to end the violence convulsing Syria.
Iran promised to stand by Syria, come what may.
First Vice President Mohammad Reza Rahimi told Iran's Press TV that Tehran's support for Syria, its main Arab ally, was "unchangeable", countering suggestions that Iran could soften its backing for Assad.
