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.
More top news
Tonight it'll be quite chilly leading to a cold but bright start.
Demonstrators jumped the barrier and lay down on the red carpet to draw attention to cuts to domestic abuse services.
Doctors in Australia have reattached 16-month-old Jaxon Taylor's head to his spine after he was 'internally decapitated' in a car accident.