Security forces fanned out through villages and towns in Syria’s northern province of Idlib on Thursday, randomly arresting men and boys older than 16 as the regime of President Bashar al-Assad worked to silence a center of anti-government demonstrations.

In this border region, where thousands of Syrian civilians have fled to havens in Turkey, Turkish officials were preparing to send food, clean water, medicine and other aid to thousands more civilians stranded on the Syrian side.

The unusual plan for a cross-border operation on Syrian soil appeared to have Syrian clearance. It was announced by Turkish Foreign Minister Ahmet Davutoglu after he met with an envoy from Assad’s government.

“We have taken precautions, and humanitarian aid will be supplied for around 10,000 people who are waiting on the Syrian side of the border,” Davutoglu said. He also reiterated Turkey’s support for major democratic reform in Syria.

The random detentions were concentrated around the major towns of Jisr al-Shughour and Maarat al-Nouman and in nearby villages, an area where the army has massed troops for days in apparent preparation for a fresh military operation, Syrian human rights activist Mustafa Osso reported. He said at least 300 people were being detained daily.

Osso also said troops opened fire early Thursday on the outskirts of Maarat al-Nouman, a town of 100,000 on the highway linking Damascus with Syria’s second-largest city, Aleppo. No casualties were reported.

Another source, the Syrian Observatory for Human Rights, said that dozens of tanks, armored personnel carriers and buses carrying security forces were deploying around the town of Khan Sheikhon, south of Maarat al-Nouman, and that residents were fleeing.

Since anti-government demonstrations erupted in mid-March, inspired by democratic revolutions in Tunisia and Egypt, Assad has unleashed the military in area after area to crush street protests. Human rights activists say that more than 1,400 Syrians have been killed and that 10,000 have been detained.

The most recent resistance, in Idlib province, appeared also to pose the most serious threat of an armed opposition base being established within Syria. Turkey is hosting 8,900 Syrians who have fled the Idlib crackdown, a refugee stream that has been an embarrassing public spectacle for Damascus, which has banned foreign journalists from covering the uprising.

Syria has appealed to the refugees to return to the flash-point town of Jisr al-Shughour, saying it is now safe. But many sound unconvinced.

Asked about the appeal, a refugee who identified himself as Ali replied: “Do you believe that? They would kill us.” He said troops were “firing at anything” in Jisr al-Shughour.

The Syrian government blames a foreign conspiracy for the unrest, saying religious extremists rather than true reform-seekers are behind it.

In Washington, the State Department reiterated U.S. condemnation of what it called the Assad government’s “revolting” actions. “Assad’s repression has only served to pour gasoline on the fire for change,” spokeswoman Victoria Nuland told reporters.

— Associated Press

Mroue reported from Beirut.