At least three Katyusha rockets fell around the northern Israeli border town of Nahariya in the morning, wounding two persons, Israeli police earlier said. Israeli army fired back with at least six artillery shells. No casualties have been reported so far.
"I can confirm that we are firing back at an area from where the rockets have been fired," the spokeswoman said.
It is still unclear who fired the rockets from Lebanon for the first time since Israel launched on December 27 a major ground offensive in the Gaza Strip aimed at stopping frequent rocket attacks on Israeli territory by Palestinian militants.
Palestinian Islamist group Hamas, which controls Gaza, has denied responsibility for the attack from Lebanon.
"We cannot blame any Palestinian faction and we don't know who fired the rockets," Hamas spokesman in Lebanon, Raafat Morra, said on Thursday.
"What is happening is the fault of Israel because it is impossible to contain the Arab and Islamic world after the Gaza massacre," he added.
According to latest reports, at least 700 Palestinians have been killed, including 215 children and 89 women, and more than 3,000 injured as a result of Israeli airstrikes and ground operations since the start of "an all-out war" against Hamas in late December.
The brief cross-border fire exchange may draw Israel into conflict with another radical Islamist group - Hezbollah - a close ally of Hamas.
A violent conflict between Israel and Hezbollah in 2006 killed over 1,000 Lebanese and about 160 Israelis. The border area in southern Lebanon is now controlled by Lebanese troops and U.N. peacekeepers.
