The Islamic State of Iraq and Syria, or ISIS, has declared a state of emergency.
The U.S. military believes the terror organization is planning a full-scale defense of its de facto capital of Raqqa in northern Syria.
There are reports that ISIS is moving equipment and fighters in and around the city, presumably in the expectation that local forces will try to capture it.
Raqqa has been an ISIS stronghold for much of the war in Syria. The terror group controls more than half of Syria.
On Friday, suspected Syrian government airstrikes in the northern city of Idlib killed at least 12 people, activists said.
The strikes came as part of an intensified air campaign launched after Islamic militants, including al Qaeda fighters, seized a central Alawite village. President Bashar Assad hails from the Alawite minority, an offshoot of Shiite Islam that has been targeted by Sunni militants throughout the civil war.
Raed Saleh, the head of a first responders group that operates in opposition-held areas, said at least 15 bodies, including those of three children, were pulled from the rubble after two airstrikes in a residential area of Idlib. He said another 38 people were wounded.
The Britain-based Syrian Observatory for Human Rights, which relies on activists inside Syria, put the death toll at 12 and said it was likely to rise.
A coalition of insurgent groups, including the al Qaeda-affiliated Nusra Front, captured Idlib and the surrounding province of the same name last year.
The airstrikes came a day after insurgents captured the village of Zaara in central Syria, where activists and government media said dozens of civilians were killed. Ahmad al-Ahmad, an activist from the nearby city of Hama, and the Observatory said airstrikes were also launched around Zaara on Friday.
Syria's state news agency SANA said government warplanes struck Nusra Front strongholds in Idlib province and Hama, killing more than 30 militants.
U.S. State Department spokesman John Kirby told reporters in Washington that initial reports of the violence in Zaara were "very, very troubling," and indicated it was based on "religious affiliation." But he said it was not yet clear who was responsible.