Four suicide car bombs struck Syrian regime targets Wednesday in the Qalamoun region near Lebanon, killing at least seven soldiers, a monitor and state news agency SANA said.
The attacks come a day after troops loyal to President Bashar al-Assad made gains in the Qalamoun area north of Damascus.
The attacks by the Islamic State of Iraq and the Levant (ISIL) and Al-Nusra Front, two Al-Qaeda-affiliated groups, came after rebels were driven out of nearby Qara village on Tuesday, said the Syrian Observatory for Human Rights.
The Observatory reported two attacks in the town of Nabek, while SANA reported two others in Deir Attiya.
"At least seven regime troops were killed in the two attacks (in Nabek) and five others are in critical condition," Observatory director Rami Abdel Rahman said.
A Syrian security source told AFP there was just one explosion at a checkpoint in Nabek.
"The soldiers at the checkpoint stopped a suspicious car and the driver, who was a suicide bomber wearing an explosive belt, tried to escape but was shot dead by soldiers," the source said.
"However, the vehicle exploded," the source added, saying there had been "victims".
Meanwhile, SANA reported two suicide attacks in front of Bassel hospital in Deir Attiya, a majority Christian town in army control north of Nabek.
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"Several guards were killed, then the terrorists broke into the hospital and tried to destroy the equipment but the army managed to chase them down," said the agency.
The Observatory said the rebels had entered the hospital and captured a wounded officer, before being thrown out by the army, leaving the man behind.
The Britain-based group did not report the two car bombs at Deir Attiya.
Loyalists backed by Lebanon's Hezbollah movement have launched a major assault on Qalamoun, a mountainous region straddling key supply lines between Damascus and Homs, as well as rebel smuggling routes criss-crossing the border with Lebanon.
Fighting raged elsewhere in Qalamoun, mainly around the rebel bastion of Yabrud, which the army shelled Wednesday, and Deir Attiya.
Warplanes launched air strikes on rebel positions around Deir Attiya, said the Observatory, while ongoing clashes killed at least eight opposition fighters.
The army had earlier said it was hunting jihadists across the region, while rebels vowed to return to Qara.
Elsewhere, a mortar round struck near central Damascus's Umayyad square, and two others hit the capital's Kassaa neighbourhood, said the Observatory.
In northern Syria's Raqa, Al-Qaeda-linked jihadists of Al-Nusra Front threw their black flag over a Shiite shrine, in yet another sign that the conflict is becoming increasingly sectarian, the group added.
An estimated 120,000 people have been killed in Syria's uprising, which began with peaceful protests against Assad in March 2011 but escalated into a full-blown insurgency after his troops launched a brutal crackdown.