Syrian air force planes fired rockets at a section of Lebanon's border with Syria on Monday, according to Lebanese security sources.
Reuters said there were no immediate reports of casualties from the strike near the town of Arsal, in the Bekaa Valley.
"Syrian planes bombed the border between Lebanon and Syria but I cannot yet say if they hit Lebanese territory or only Syrian territory," a high-ranking Lebanese army official told Agence France-Presse.
Many of the residents in Arsal, in east Lebanon, support the Syrian rebels fighting against Syrian President Bashar al-Assad's government.
Al-Manar television, belonging to the pro-Syrian Lebanese Shiite Hezbollah movement, said the warplanes targeted two barns used by "armed men," according to AFP.
Syria's Foreign Ministry said last Thursday that a "large number" of Syrian rebels had crossed the Syria-Lebanon border into the Syrian town of Tel Kalakh last week, Al Jazeera noted.
"Syria expects the Lebanese side to prevent these armed terrorist groups from using the borders as a crossing point, because they target Syrian people and are violating Syrian sovereignty," Syria told the Lebanese government, according to state media.
Lebanon has a policy of "dissociation" from the Syrian civil war, though officials feel their country is being drawn into the conflict.
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