BEIRUT: Syrian troops shelled rebel strongholds on the edge of Damascus from multiple rocket launchers based on hilltops Tuesday, while the battle intensified for control over Aleppo’s international airport in Syria’s north, activists said.

Fierce fighting also raged for a second day as rebels tried to take back the impoverished neighborhood of Bab Amr in central Homs.

As the bloodletting is close to entering its third year without a solution in sight, France and Britain raised the pressure on other European Union members to lift an arms ban to supply weapons to the rebels if it would help topple President Bashar Assad.

Regime forces killed at least 30 army deserters in an ambush on the Damascus Airport road as opposition fighters were guiding them on foot to a rebel-held district, opposition sources said.

The thud of artillery and mortars reverberated across the capital from the fighting in the northeastern neighborhoods of Jobar and rebel-held areas south of the capital. Activists said several people were wounded.Opposition fighters have stepped up mortar attacks on Damascus in recent weeks, striking deeper than ever into the heart of the city. Rebel fighters tried in the past to establish bridgeheads in Damascus but were pushed back to the suburbs by regime forces.

The defected soldiers were killed after being ambushed as they crossed the highway to rebel held Eastern Ghouta, a rebel commander in the region said.

“They ambushed them at 2 a.m. The regime had intelligence that they were coming,” another opposition source said, adding that seven other members of the group of 40 had been wounded.

An opposition military source said rebels over the weekend had overrun a missile squadron manned mostly by Alawites in the town of Khan al-Sheih near Damascus, and killed at least 30 of its troops who had escaped to a nearby farm.

“The rebels captured air-to-surface missiles, which they cannot operate, and 11 anti-aircraft guns, which they can,” the source said.

In Homs, fresh violence broke out on the outskirts of Bab Amr, which had become a symbol of resistance to Assad’s regime before it was overrun by the army a year ago. “Troops launched rockets from the Baath university into parts of Bab Amr,” said the opposition Syrian Observatory for Human Rights activist group.

Once an opposition bastion, Bab Amr was seized by the army from rebel hands last year after a relentless, monthlong bombing campaign on the neighborhood in which hundreds of people were killed. Sunday, rebels pushed back into Bab Amr, and Syrian forces responded by firing heavy machine guns into the neighborhood, sending residents fleeing.

In northern Aleppo, rebels renewed a push to capture the city’s international airport and other nearby air bases as part of their campaign to erode the regime’s air supremacy.

The army holds large parts of Aleppo and maintains control over the airport, the country’s second largest. Crucially, Syria’s airspace is firmly controlled by the regime in Damascus, which uses its warplanes to bomb rebel strongholds.

The Observatory said clashes erupted around the airport again Tuesday, while rebels intensified their assault on the Nairab and Mannagh air bases near the strategic facility, which has not been handling flights for weeks because of the fighting.

The rebels control large swathes of territory outside of Aleppo, but the battle for the city itself, Syria’s main commercial hub, is locked in a stalemate. Rebels pushed into the city in July and captured several neighborhoods. It has been a major battleground in the civil war ever since.

With no end in sight to the spiraling violence, France said it was working with Russia and the United States to draw up a list of regime officials with whom the opposition can negotiate.

French Foreign Minister Laurent Fabius said, “We worked together on an idea ... of a list of Syrian officials who would be acceptable to Syria’s opposition National Coalition.”

Opposition chief Ahmad Moaz al-Khatib has offered to talk to regime representatives without “blood on their hands.”

Britain said it would consider ignoring a European Union arms ban and could supply weapons to rebels if it would help topple Assad. Prime Minister David Cameron said he hoped London could persuade its EU partners “if and when it becomes necessary [to provide weapons] they’ll agree with us.”

Last month, the EU amended its embargo to allow members to supply “non-lethal” equipment and training to the opposition but stopped short of lifting the embargo entirely. Officials have also privately indicated that some training of rebels, with support and possible limited participation of Americans, is going on in neighboring countries.

Asked whether Britain would veto the arms embargo when it comes up for renewal in three months, Cameron told a parliamentary committee he would “like to continue with an EU approach.”

“But if we can’t, then it’s not out of the question we might have to do things in our own way. It’s possible.”

France’s Foreign Minister Laurent Fabius, meanwhile, hinted it would push to have the embargo lifted. “France is thinking – although it is a European decision – of going further in lifting the embargo,” Fabius told a parliamentary committee.

The EU is split over arming the rebels. Britain, France and Italy are tipping in favor of it, while Germany and others warn against it.

In the U.S., the Director of National Intelligence James Clapper said while forces seeking to oust Assad were gaining strength and territory, the Syrian opposition remained fragmented and was grappling with an infusion of foreign fighters.

Assad’s government is losing territory and experiencing shortages in manpower and logistics, Clapper said. But at the same time, there were “literally hundreds” of cells of opposition fighters over which leaders were struggling to impose more centralized command and control.

U.S. intelligence agencies do not know how long Assad will keep his hold on the country, Clapper told a Senate Intelligence Committee on global security threats. “The question comes up, ‘How long will Assad last?’ And our standard answer is, ‘His days are numbered. We just don’t know the number.’ Our assessment is that he is very committed to hanging in there and sustaining his control of the regime,” Clapper told the Senate panel.