There have been several clashes in Lebanon between pro and anti-Syrian factions in which several people have died. The tensions between the two sides is reminiscent of how the bloody civil war of the 70's and 80's tore Lebanon apart.
Now Syrian forces are firing into Lebanon and pursuing rebels who have established bases along Syria's northern border inside Lebanon.
In contrast with Turkey, which openly harbors rebels fighting to topple Syrian President Bashar al-Assad, Lebanon was not expected to respond militarily and has played down the effect of regular clashes along the frontier.
But rebels have used north Lebanon as a base and Assad's forces have at times bombed villages and even crossed the border in pursuit of militants, threatening to inflame tensions in Lebanon given a long history of Syrian domination there.
Residents of Lebanon's Wadi Khaled region said several mortar bombs hit farm buildings five to 20 km (3 to 12 miles) from the border at around 2 a.m. At midday villagers reported more explosions and said they heard gunfire close to the border.
In the village of al-Mahatta, a house was destroyed, killing a 16-year-old girl and wounding a two-year old and a four-year old, family members told Reuters. A 25-year-old woman and a man were killed in nearby villages, residents said.
The Lebanese army issued a brief statement about the incident. There was no immediate response from the prime minister or the foreign ministry, both of whom have expressed fears that Lebanon could be dragged into the conflict.
Because of anti-Assad sentiment in Lebanon, the Hezb'allah dominated government has been forced to side with the rebels. But there are reports that some Hezb'allah fighters have joined Assad's forces in trying to crush the rebellion. Assad is Hezb'allah's conduit for arms from Iran and they are not likely to abandon him so lightly.