The attacks came almost a week after Hassan Nasrallah, the leader of Hezbollah, announced his military support for the government of President Bashar al-Assad of Syria. Syrian opposition groups, which aim to overthrow Mr. Assad, condemned Mr. Nasrallah’s stand and called for his fighters to withdraw from Syrian soil. Some rebel brigade leaders threatened to retaliate against Hezbollah directly.

Indiscriminate shelling has hit the smaller Shiite village of Hermel, in northeastern Lebanon, in recent weeks, killing several civilians. But Friday night’s rockets could be the most provocative yet, hitting a major population center in the northeastern Bekaa Valley. Baalbek is apparently the furthest south in the Bekaa that shells from Syria targeting Hezbollah areas have reached.

Baalbek is home to one of Lebanon’s most important archaeological sites and tourist destinations, the Baalbek ruins, which include a pre-Hellenic temple and later Roman structures. It is also the site of an annual summer music festival that draws people from all over the region. Unrest in the Bekaa Valley would further hurt the Lebanese tourist and agricultural economies, which have already been devastated by the Syrian crisis.