GUVECCI, Turkey - More than 4,000 Syrians have fled to Turkey to escape a crackdown on protests against President Bashar Assad and thousands more are sheltering near the border, officials and activists said on Saturday.Fearing revenge from security forces for clashes in which authorities said 120 troops were killed this week, the refugees streamed out of the northern town of Jisr al-Shughour ahead of a military operation launched by the army there on Friday.RELATED:UK, France put forward UN resolution condemning SyriaSyrian army pushes into border town, state TV saysA senior Turkish diplomat said 4,300 Syrians had crossed the border and that Turkey was prepared for a further influx, though he declined to predict how many might come."Turkey welcomed a great many number of guests in the past in their times of most dire need. We can do that again," Foreign Ministry Deputy Undersecretary Halit Cevik was quoted as saying by state-run Anatolian news agency.Witnesses in the border province of Hatay said a tent hospital was being set up at the site of one of the refugee camps, and Radikal newspaper said Turkey would establish a buffer zone if migrant inflows from Syria exceed 10,000. Just inside Syria, thousands more people were gathering close to the frontier, according to an activist helping coordinate the movement of refugees."The border area has turned practically into a buffer zone," said the man, who identified himself only as Abu Fadi. "Families have taken shelter under the trees and there are 7,000 to 10,000 people here now."Human rights groups say security forces have killed more than 1,100 Syrian civilians in an increasingly bloody crackdown on demonstrations calling for Assad's removal, more political freedoms and end to corruption and poverty.Thirty-six protesters were shot dead across Syria on Friday, activists said. Syrian authorities deployed helicopter gunships in the town of Maarat al-Numaan, they added, in the first known use of air power against unrest.The government, which has blamed violence in the protest wave on "terrorists", said on Saturday the army had arrested two armed groups in Jisr al-Shughour after launching operations there in response to requests from residents. The state news agency SANA said they seized guns, explosives and detonators.Some activists and residents said the fighting earlier in the week in Jisr al-Shughour was between members of the security forces after some mutinied over orders to shoot at protesters, and that many of the dead were civilians caught in the clashes.Damascus has banned most foreign correspondents from the country, making it difficult to verify accounts of events.The northwest border area, like other protest hotspots, is prone to tension between Syria's majority Sunni Muslims and Assad's Alawite sect, which dominates the Syrian power elite. The recent clashes hint at splits within the security forces, whose commanders are mainly Alawite and conscripts Sunni.The protests were inspired by uprisings against other entrenched autocrats in the Arab world but do not appear to have become large or widespread enough to threaten Assad with the same fate as the toppled leaders of Egypt and Tunisia.