"The Lebanese army... is mourning a number of troops who were martyred in clashes that pitted the military against terrorist groups near Ras Baalbek," said the statement, which went on to list the names of the killed.
Among them was Lieutenant Ahmad Mahmud Tabikh, said the army.
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The clashes erupted in the Ras Baalbek area early on Friday, after around 200 gunmen coming from the Qalamun region of Syria attacked a Lebanese military post, according to a security source.
The border clash was the latest violence between the Lebanese military and militants on the border with Syria.
Syria's civil war has regularly spilled into Lebanon, with jihadists briefly overrunning the eastern Lebanese town of Arsal in August after running gun battles with the army.
The jihadists withdrew after a ceasefire, but took with them several dozen hostages from the Lebanese army and police, four of whom have since been executed.