Government troops massed outside Jisr al-Shughour, the scene of recent demonstrations, fleeing residents said on Thursday, adding the settlement was now largely deserted.
The latest reports of a government crackdown intensified international concerns over Syria's handling of pro-democracy protests, inspired by uprisings across the Arab world.
Britain, France, Germany and Portugal have asked the U.N. Security Council to condemn Assad although veto-wielding Russia has said it would oppose such a move.
World powers have shown no appetite for any Libya-style military intervention in Syria, which has so far shrugged off sanctions and verbal reprimands.
Residents on Thursday said about 40 tanks and troop carriers had deployed about 7 km (4 miles) from Jisr al-Shughour, a northwestern town of 50,000 where authorities say "armed gangs" killed more than 120 security personnel earlier this week.
Turkey's Red Crescent said it was setting up a second camp near the border to shelter people still crossing the border to escape the military build-up.
Turkish Foreign Minister Ahmet Davutoglu on Thursday said 2,400 people had already crossed into Turkey.
"Jisr al-Shughour is practically empty. People were not going to sit and be slaughtered like lambs," said one refugee who crossed on Wednesday and who gave his name as Mohammad.
FRIGHTENED REFUGEES CROSS TO TURKEY
Turkish authorities have denied media access to the refugee camps, set in a picturesque valley. Behind the gates, rows of large white tents, could be seen some with washing strung between them, and children playing.
Syria has also barred most independent media from the country, making it difficult to verify accounts of the violence.
Assad, 45, has promised reforms, even while cracking down on unrest that has become the gravest threat to his 11-year rule. Friday prayers have been a focus of protests throughout the uprising.
The U.N. nuclear watchdog board reported Syria to the Security Council for covert atomic work, diplomats said on Thursday, a U.S.-led move coinciding with Western condemnations of Damascus' crackdown on opposition protests.
Russia and China voted against the proposal, probably ruling out any follow-up punitive measures
