Islamic State jihadists, building on vast land grabs in Iraq, have seized an army position in the Syrian city of Hasakeh, a monitoring group said Sunday.
On another front in Syria's complex civil war, rebels seeking President Bashar al-Assad's ouster captured a weapons depot in Hama province, said the Syrian Observatory for Human Rights.
And in the central city of Homs, a car bombing killed seven people, the Observatory and state media said.
In Hasakeh in the northeast, "IS jihadists took over the army's Regiment 121 (base) at Maylabiyeh" after a three-day battle, said the Britain-based Observatory.
On Twitter, supporters of IS, which first emerged in Syria's war in spring 2013, celebrated the army position's "liberation" at the hands of the jihadists.
The latest advance came a day after IS took over a Division 17 position in Raqa province, killing at least 85 regime troops there, including 50 who were executed after their capture.
But also on Saturday, the regime recaptured the Shaar gas field in Homs province in central Syria, where IS reportedly killed 270 people while taking the site.
While IS has escalated its offensive against the regime in parts of Syria in the past two weeks, it has also been in a state of open war since January against rebels seeking Assad's ouster.
On Sunday, IS killed 15 Syrian rebels in an ambush as the jihadists tried to advance on Aleppo province, Observatory director Rami Abdel Rahman said.
"IS is very ambitious. It wants to capture both the regime-held Kweiris airport (in Aleppo province), and ultimately Aleppo city -- both the opposition and regime-held areas," Abdel Rahman said.
- Emboldened by Iraq offensive -
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In June, the jihadist group proclaimed an Islamic "caliphate" straddling Syria and Iraq.
"IS has nothing to do with the anti-Assad revolt. It just wants control," said Abdel Rahman.
It was emboldened by a June offensive in Iraq when swathes of the north and west fell out of Baghdad's control.
Syrian rebels say the group transported a large amount of heavy weapons captured from fleeing Iraqi troops into Syria.
On another front, rebels in Hama province captured Khattab and Rahbeh villages, taking over arms depots, Abdel Rahman said.
Rebels, he added, are now "advancing towards Hama military airport".
The air base is important because aircraft loaded with deadly barrel bombs regularly take off from there to attack opposition areas in Hama and Idlib provinces.
Amateur video posted by activists on YouTube showed some of the weapons seized by the rebels in Hama, including rockets, ammunition and mortars.
Meanwhile in Homs city, seven people were killed and 20 wounded in a car bomb attack on an Alawite district, said the Observatory.
Immediately after the blast, several home-made rockets hit the neighbourhood.
State media also reported the explosion, giving the same death toll, but claimed the blast was caused by a suicide car bomb attacker.
Homs was once dubbed "the capital of the revolution" against Assad, but all except one district are now squarely in regime control.
Syria's war has killed more than 170,000 people since it broke out in March 2011 and forced nearly half the population to flee their homes.