Fighting raged around Damascus on Friday and Internet and phone links in Syria remained cut for a second day, as the capital's international airport reopened to flights after heavy clashes in the area.
Delegates from more than 60 countries, meanwhile, were gathering in Tokyo to find ways to step up the pressure on President Bashar al-Assad's regime.
The Syrian Observatory for Human Rights said the road from the capital to Damascus airport had reopened, a day after fighting during which a bus carrying airport employees was hit by a shell, killing two people.
A security source also reported the deaths, blaming rebels for the shelling, but SyrianAir director Ghida Abdellatif said that the two employees had escaped with injuries.
The United Nations said four of its staffers were also wounded when their bus was targeted by gunfire on its way to the airport on Thursday.
Air traffic resumed on Friday and the 27-kilometre (17-mile) road between the airport and the capital reopened after a night of heavy clashes between rebels and troops in the area, airport sources said.
A military source in Damascus said the army had taken control of the western side of the road leading to the airport and a small portion on the east by dawn, allowing travellers to move through.
“But the most difficult part is yet to come. The army wants to take control of the eastern side, where there are thousands of terrorists and this will take several days,” he said, using the term regime officials use for rebel fighters.
At least 15 civilians were killed in a military offensive and clashes around Damascus on Friday, including in the southeast near the airport road and in Daraya to the southwest, the Observatory said.
Warplanes pounded the northeastern town of Irbin amid shelling of orchards in the south of the capital, all opposition strongholds where rebels have rear bases, it added.
The army, meanwhile, withdrew from Omar oil field, one of the last regime positions east of Deir Ezzor city near the Iraqi border, giving rebels control over the country's major fields.
Rebels last week gained a huge stretch of territory east of Deir Ezzor city along the Iraqi border, now the largest outside government control.
The Assad regime has been reducing its territorial ambitions to focus on Damascus, central Syria and Alawite bastions, as it digs in for a long war, according to analysts.
In the town of Tal Kalakh on the border with Lebanon, 17 young Sunni volunteers from the Lebanese city of Tripoli were killed on Friday, a Lebanese security source and a Muslim leader said.
The security source said he was informed of the deaths of the men “who went to Syria to fight with the rebels and were all killed in a trap in Homs province.”
The Observatory, which reported an initial toll of 39 killed nationwide on Friday based on information from activists and medics on the ground, said most phones and Internet networks were down for a second straight day.
AFP correspondents noted that Internet and telephone communications, including mobile phones, were cut in the capital.
But State Department spokeswoman Victoria Nuland said that some 2,000 communications sets supplied to opposition rebels over recent months as part of a US non-lethal assistance programme were not affected by the blackout.
France on Friday urged Syrian authorities to immediately restore the phone and Internet networks, charging the blackout was proof that the regime was trying to “hold its people hostage.”
“We urge the Damascus regime to immediately re-establish communication links,” foreign ministry spokesman Philippe Lalliot said. “It is a matter of serious concern for us.”
In Tokyo, delegates from more than 60 countries gathered for a meeting to ramp up pressure on Assad.
Japanese Foreign Minister Koichiro Gemba told the “Friends of Syria” group that the international community had to act together where the divided UN Security Council had failed.
“While the United Nations Security Council has been unable to assume its primary responsibility, it's increasingly important for the international community to act as one in order to deal with” the continuing violence, he said. - Sapa-AFP