Syrian security forces have expanded their assault on cities and villages in the country's northwest, as detentions continue and scores of people continue to flee to the border with Turkey.

Residents and rights groups said Thursday that the Syrian military had deployed dozens of tanks, armored personnel carriers and trucks around Khan Sheikhun, a town in Idlib province.

The operation is part of the latest effort in the weeks-long campaign by President Bashar al-Assad to suppress the anti-government protests that are threatening his 11-year rule.

Activists told the Associated Press that Syrian security forces have been randomly rounding up males over age 16. They told AP the detentions were concentrated in and around the major towns of Jisr al-Shughour – which elite forces occupied Sunday – and Maaret al-Numan, where the army has massed troops for days in apparent preparation for a fresh operation.

World powers have widely condemned the Syrian crackdown.

On Thursday, United Nations Secretary-General Ban Ki-moon said he had spoken to Mr. Assad and urged him to “stop killing people.”

U.S. State Department spokeswoman Victoria Nuland called the government crackdown “revolting” and “barbaric.” In a Thursday briefing, she also said the U.S. has been increasing its contacts with Syrians inside and outside of the country who are seeking change.

In Ankara, Turkish officials, faced with caring for more than 8,900 Syrian refugees staying in makeshift tents, pressed an Assad envoy, Hassan Turkmani, to end the military campaign against the protesters.

After a Thursday meeting with the Syrian envoy, Turkish Foreign Minister Ahmed Davutoglu said his country is also extending assistance to about 10,000 people who have massed along the Syrian side of the border.

Also Thursday, Syrian state television said telecoms tycoon Rami Makhlouf, a cousin of the president, will quit his businesses and allocate profits to charity. Makhlouf controls several companies, including Syria's largest mobile phone operator, duty free shops, an airline and shares in at least one bank.

He is widely despised by government opponents for allegedly exploiting his relationship with Mr. Assad to build his commercial empire and cited in their calls for an end to official corruption.

Makhlouf is facing both European Union and U.S. sanctions.

On Wednesday, hundreds of Syrians fled the northern town of Maarat al-Numan ahead of a feared military assault. Witnesses and activists say Syrian troops intermittently shelled areas near the city and raided nearby villages, making arrests.

Army units have also surrounded the eastern town of of al-Boukamal near the Iraqi border, where clashes have broken out between protesters and Assad loyalists. Forces also entered nearby Deir al-Zour, one of Syria's largest cities, where protests continued.

Rights activists say 1,300 civilians and 340 security force members have been killed since the protests against Mr. Assad's government began in mid-March. About 10,000 people have been detained.