A Syrian helicopter fired on an area on the outskirts of a Lebanese town on Wednesday, a Lebanese security official told AFP on condition of anonymity.
"A helicopter fired two rockets on Jubaneh al-Shmis on the outskirts of Arsal. The area lies several hundred metres (yards) away from a Lebanese army checkpoint," the official said on condition of anonymity.
Arsal is a majority Sunni town in northeastern Lebanon, many of whose residents support the revolt against President Bashar al-Assad in neighbouring Syria.
The area lies on the border with Syria, and has become home to thousands of people fleeing their the conflict.
Scores of Syrians injured in the violence have been brought into Arsal for medical treatment in recent months, and there have been reports of fighters and arms being smuggled in.
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A local official in Arsal confirmed reports of Wednesday's cross-border attack.
"Two rockets were launched, though no casualties were caused. There are several houses in the area where the rockets landed," said Ahmad Fliti, deputy mayor of Arsal.
The attack comes after reported air strikes in the same area last month, which were condemned by Lebanese President Michel Sleiman and the United States. Damascus denied responsibility for the attacks.
Syria's conflict, which has raged for more than two years, further entrenching deep divisions in Lebanon.
While Lebanon's Sunni-led March 14 movement supports the rebels, the powerful Shiite movement Hezbollah and its allies back the Assad regime.