At least four rockets fired from Lebanese territory have hit Israeli towns close to the border without causing casualties.
Several people were treated for shock in Kiryat Shmona
Three of the Katyusha rockets slammed into Kiryat Shmona, directly hitting one house and knocking out electricity, while a fourth hit the town of Shlomi.
Israeli army sources blamed Lebanon's Hezbollah group but there was no confirmation from the militants.
The border zone has been tense since Israel left south Lebanon in 2000.
Israeli television showed the remains of what appeared to be a Katyusha rocket in Kiryat Shmona along with holes in the ground and in the side of a house.
Three houses in all were damaged and three people were treated for shock but the only injury caused was to a dog, Israel's Haaretz newspaper reports.
Residents were temporarily ordered into shelters and the electricity was out for half an hour.
The site of the single rocket impact in Shlomi was still being investigated.
At least seven rockets were launched from Lebanese territory, Lebanese police were quoted as saying by AFP news agency.
Hezbollah has fired Katyusha rockets into Israel before
Two were fired from the western sector, 20km (12 miles) south-east of Tyre, and five others from the eastern sector on Aadaysse hill, they added.
A Hezbollah spokesman told the agency he knew nothing of the attacks while a Palestinian Fatah movement official in Lebanon, Sultan Abu Aynaeyn, strongly denied any involvement by Palestinians.
Last month Israeli fighter jets attacked a Hezbollah command post in response to an attack on an Israeli border community.
Hezbollah, which fought a guerrilla war against Israel's 18-year occupation of Lebanon's southern border, frequently targets Israeli troops in the disputed Shebaa farms area.
Israel helicopters have been patrolling the area since Tuesday evening's attacks.