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.
In Hasake, northeast Syria, "IS jihadists took over the army's Regiment 121 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 Division 17 in Raqa province.
According to the Observatory, at least 85 regime troops were killed during the IS takeover, among them more than 50 who were executed after their capture.
But also on Saturday, the regime recaptured Shaar gas field in Homs province of central Syria.
IS had captured the field nearly two weeks ago, reportedly killing 270 guards, pro-regime paramilitary and civilian employees.
While IS has escalated its offensive against the regime in parts of Syria in the past two weeks, it has been at open war since January against rebels seeking Assad's ouster.
In June, the jihadist group proclaimed an Islamic "caliphate" straddling Syria and Iraq.
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 IS transported a large amount of heavy weapons captured from fleeing Iraqi troops into Syria.
On another front, Syrian rebels in Hama province captured Khattab and Rahbeh villages, taking over arms depots, said Observatory director Rami Abdel Rahman.
Rebels, he added, are now "advancing towards Hama military airport", a key army position and site of one of Syria's most feared prisons.
Amateur video posted by activists on YouTube showed some of the weapons seized by the rebels in Hama, including rockets, ammunition and mortars.
The Observatory, meanwhile, said the death toll from a car bomb attack on Saturday in Atme, on the Turkish border, has risen to nine, among them an Islamist rebel commander.
Another seven people were killed in a separate car bombing the same day in Azaz, also on the Turkish border, the group said.
State television said a "terrorist suicide car bomb attack" hit Homs city in the heart of the country Sunday, causing an unknown number of casualties.
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.