Al Jazeera's Rula Amin, monitoring developments from Beirut, said it was the third time rockets had been fired from Lebanon into Israel since the military assault on the Gaza Strip.
She said officials of Hezbollah, the Lebanese group, had told her that they did not need to issue a denial "because when they do something they usually claim responsibility".
Hezbollah and Israel fought a war in the summer of 2006.
Fouad Siniora, the Lebanese prime minister, in a statement described the Israeli shelling as an inexcusable breach of Lebanon's sovereignty.
He reaffirmed Lebanon's commitment to the UN Security Council resolution 1701, saying the attack was a threat to the country's security and stability and a breach of the resolution.