Syrian security forces are continuing their assault on cities and villages in the country's restive northwest, as world leaders are condemning the crackdown.

The Syrian news agency Sana and rights activists said Thursday that military units equipped with dozens of tanks and armored personnel carriers deployed near Khan Sheikhoun, circled Maarat al-Numaan and attacked two more villages, Shughur al-Kadima and Janudiyeh.

Hundreds of Syrians fled their homes to escape across the border into Turkey. Some said Syrian troops fired random shells at the villages and ransacked their homes.

The latest violence is part of the weeks-long assault by troops loyal to President Bashar al-Assad on anti-government protesters seeking to end his 11-year reign. More than 1,300 civilians and 340 government troops have been killed since mid-March, but Mr. al-Assad has continued the crackdown over the increasingly vocal objections of world leaders.

On Thursday, United Nations Secretary-General Ban Ki-moon called on the Syrian president to “stop killing people” and negotiate with the protesters “before it's too late.”

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

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-Numaan, where the army has massed troops for days in apparent preparation for a fresh operation.

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 extending assistance to about 10,000 people who have massed along the Syrian side of the border.

Also Thursday, Syrian state television said telecom 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.