A car bomb rocked Syria's third largest city Homs on Sunday killing 15 people, state media said, as the army hammered rebel positions around Damascus in a strategic assault aimed at securing the capital.
Shell fire from Syria, meanwhile, hit a Turkish border town late Saturday, without causing casualties. It was the first cross-border shelling since Ankara requested that NATO deploy Patriot air defence missiles on the restive frontier.
"A terrorist attack struck the Hamra district of Homs," the state SANA news agency said, adding that it killed 15 people and wounded 24 in the government-held neighbourhood. State television said it was a car bombing.
The Syrian Observatory for Human Rights also reported a car bombing in Homs.
"The blast hit an area where there is a large vegetable market," the Britain-based watchdog said.
"The Hamra neighbourhood has been under regime control throughout the revolt," its director Rami Abdel Rahman told AFP.
Amateur video footage posted online by opposition activists showed the bodies of at least three victims, including a woman buried in the rubble of a building as a car burned not far away.
Another video showed an injured child lying in hospital, wailing in pain.
Straight after the attack, hundreds of people started to protest against President Bashar al-Assad, according to activists, with some blaming the regime for the bomb attack.
Homs was one of the cradles of the armed uprising against Assad's rule, earning it the monicker of "capital of the revolution" from opposition activists.
The city suffered devastating violence earlier this year, but in recent months the army has opted to keep mainly Sunni Arab rebel-held districts around the centre under siege rather than launch an all-out assault.
Assad's forces pounded rebel positions around Damascus with artillery fire and air strikes, in an offensive aimed at securing a perimeter around the capital including the main highway to the international airport that has been under sustained rebel assault, the Observatory said.
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"The Syrian army has opened since Thursday morning the gates of hell to all those who even consider getting close to Damascus or of attacking the capital," pro-regime newspaper Al-Watan said.
Fierce fighting erupted in several villages in the eastern suburbs and the army shelled rebel positions in the larger towns of Douma and Harasta, as troops sought to secure the airport highway, the Observatory said.
Flights from the airport resumed only on Friday, a day after a series of attacks on traffic on the 27-kilometre (17-mile) road from the capital, one of them deadly, were brought to an end by a major ground assault.
But a military source said several more days of fighting were needed to fully secure the highway.
Nationwide, at least 134 people were killed on Sunday, among them 58 civilians, the Observatory said. They add to a death toll that already tops 41,000 over the past 20 months.
On the Turkish border, tensions flared for the first time since Ankara asked its NATO allies for the deployment of Patriot missiles last month in the wake of a series of cross-border fire incidents, some of them bloody.
Shells fired from Syria hit the Turkish border town of Reyhanli late Saturday amid clashes between Assad's troops and rebels around the nearby Bab al-Hawa border post, Turkey's state-run Anatolia news agency reported.
They caused no casualties, it said, without specifying whether Turkish forces had retaliated as they have to previous incidents.
Damascus has reacted furiously to Ankara's appeal to NATO, accusing it of bringing the violence upon itself by giving shelter to the rebels and funnelling arms deliveries from Gulf Arab states with Western blessing.
NATO foreign ministers meeting on Tuesday and Wednesday in Brussels are expected to signal support for Turkey by giving the go-ahead to deploy the missiles, diplomatic sources in Brussels said.
Unidentified Syrian gunmen fired shots across the border on a Lebanese military post on Sunday drawing returning fire, an army statement said.
It said there were no reports of casualties but the incident highlighted growing international concern of the potential for the Syrian conflict drawing in its neighbours.