BEIRUT, March 18 (Reuters) - - Lebanese demonstrators blocked several roads throughout the country on Tuesday evening in protest at what they called a "siege" on the Sunni Muslim town of Arsal on the border with Syria.
The road to Arsal was blocked by residents of the Shi'ite Muslim town of al-Labwa who erected sand barriers this weekend, a security source said, cutting it off from other parts of Lebanon.
The blockade follows days of rocket attacks on Labwa which residents blame on Sunni rebels who have fled Syrian President Bashar al-Assad's forces into Arsal, where tens of thousands of refugees live.
The border area has been steadily sucked into Syria's three-year-old conflict as Syrian troops and jets target rebel bases on the frontier and suspected Syrian rebels fire rockets at Shi'ite towns to punish the Shi'ite Lebanese militant group Hezbollah for supporting Assad.
On Tuesday, the army fired shots in the air to disperse Sunni protesters who blocked a main road leading from the capital Beirut to the southern costal town of Sidon, where residents also reported protests.
Some of the protestors in Beirut wore black masks and the security source said demonstrators also barred roads in Sunni areas in the Bekaa Valley, where Arsal is located.
Tensions have been especially high in and around Arsal after Syrian forces and Hezbollah gunmen recaptured the border town of Yabroud from Sunni Muslim rebels on Sunday.
The rebel defeat at Yabroud sent a stream of refugees and fighters across the border into Arsal, and was followed hours later by a suicide car bombing against a local stronghold of SHezbollah.
The rebel loss of Yabroud could exacerbate sectarian tensions across Lebanon, already struggling with the fallout of Syria's civil war. (Reporting by Oliver Holmes; Editing by Mark Heinrich)