The Israeli military says its warplanes are hitting Hezbollah targets in Lebanon after detecting moves to fire missiles and rockets into Israel.
"In a self-defence act to remove these threats, the IDF (Israel Defense Forces) is striking terror targets," IDF spokesman Daniel Hagari said.
Israel said Lebanese civilians had been warned to immediately leave areas where Hezbollah, an Iran-backed Shia Muslim group, was operating.
Across northern Israel sirens warning of incoming rockets were heard sounding.