Mahmood Khazaal, former mayor of the Lebanese border town of al-Buqaya, said 1,500 people had come on foot. Many crossed a river dividing the two countries because Syrian authorities had stopped them leaving through official border crossings.
"They are leaving their houses and their men. The women have come with their children," Khazaal told Reuters. "We heard shooting since 6.15 (1515 GMT Wednesday) and that`s when they started fleeing."
It was not clear how many people were hurt in the clashes.
"We fled from the shooting in the Tel Kelakh region," said one woman, who declined to give her name, referring to the area around a Syrian border town. "There was shooting which forced us to leave our country and flee. Our men are still surrounded."
Syria has been hit by six weeks of protests against the rule of President Bashar al-Assad. A Syrian rights group said on Thursday at least 500 people had been killed in the unrest.
Khazaal said Lebanese security forces were helping the Syrian familes cross over. A Lebanese security source said the army had stepped up patrols in the area. (S008/K004)