Both Aljazeera and Haaretz are reporting that rockets have hit towns in northern Israel. The source of the rockets is said to be lebanon:
Per Haaretz
At least three Katyusha rockets, fired from south Lebanon, landed in northern Israel early Thursday morning.
A medical official said several people were lightly wounded. Channel 10 reported that five people were lightly wounded or suffered shock.
-- snip --
Residents of the western Galilee on Wednesday reported that three rockets hit their communities, with one falling near Nahariya.
Channel 1 reported that several northern residents have opened their bomb shelters.
I would like to emphasize that it has not yet been confirmed who fired said rockets.
[UPDATE]: Haaretz news-ticker has the following:
08:24 Channel 10: IDF striking targets in southern Lebanon (Haaretz)
8:24 is their local time.
[UPDATE II]: According to an Al-Jazeera reporter, Israeli sources are saying that it might not be Hezbollah. (via Al-Jazeera news-ticker)
[UPDATE III]: Haaretz news-ticker:
08:51 Lebanese sources: Palestinians fired rockets at north Israel, not Hezbollah (Ch. 10)
08:50 Lebanon: Rockets fired by Palestinian groups, not Hezbollah (Channel 10)
[NOTE]: I removed the following fro the opening paragraph since it is more likely to be not the case according to the most recent news reports: "It seems that Hezbollah is now part of the conflict."