The Syrian government recently warned Lebanese officials it would respond with military force to any cross-border aggression. Violence along the Lebanese-Syrian border has involved pro- and anti-Syrian government forces.
The Cedar Revolution in 2005 broke Syria's grip on Lebanese affairs. Spill-over concerns have mounted as the Syrian civil war entered its third year, however.
No casualties were documented by Human Rights Watch in a weekend border attack. The organization said two civilians died and four others were injured in a July border strike.
Deputy Director of Middle East programs Nadim Houry said, even if there are fighters on Lebanon's side of the border, there's no justification for attacks on residential areas.
"All sides need to take all feasible precautions to protect civilians," he said in a statement.
The Lebanese government said it would file a complaint with the Arab League after a rocket attack left one person dead in the border town of al-Qasr last week.
Syrian Ambassador to Lebanon Ali Abdel-Karim Ali said the government has received notices but nothing formal.
"Security in border areas will almost certainly deteriorate unless the government takes measures to secure such areas," Houry warned.