Syrian forces were believed to be chasing rebels across the border with Lebanon when they fired into the border town of Arsal.
Arsal is a predominantly Sunni Muslim town, like the majority of Syria's opposition that is trying to oust President Bashar Assad from power. Assad belongs to the minority Alawite sect, an offshoot of Shiite Islam.
Lebanese armed forces have in the past detained people in the region for trying to smuggle weapons into Syria from Lebanon.
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Highs of 7 Celsius (45F).
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