Israel shot down a drone Thursday as it approached the country's northern coast, the military said. Suspicion immediately fell on the Hezbollah militant group in Lebanon.
The incident was likely to raise already heightened tensions between Israel and Hezbollah, a bitter enemy that battled Israel to a stalemate during a monthlong war in 2006.
Prime Minister Benjamin Netanyahu, who was in northern Israel at the time of the incident, said he viewed the infiltration attempt with "utmost gravity."
"We will continue to do everything necessary in order to protect the security of the citizens of Israel," he said.
Lt. Col. Peter Lerner, a military spokesman, said the unmanned aircraft was detected as it was flying over Lebanon and tracked as it approached Israeli airspace.
Lerner said the military waited for the aircraft to enter Israeli airspace, confirmed it was "enemy," and an F-16 warplane shot it down.
The drone was flying at an altitude of about 6,000 feet and was downed roughly five miles off the Israeli coast near the northern city of Haifa. Lerner said Israeli naval forces were searching for the remains of the aircraft.
He declined to say who sent the drone. But other military officials, speaking on condition of anonymity because they were not permitted to talk to the media, said they believed it was an Iranian-manufactured aircraft sent by Hezbollah. Hezbollah sent a drone into Israeli airspace last October that Israel also shot down.
Netanyahu was informed of the unfolding incident as he was flying north for a cultural event with members of the country's Druse minority. Officials said his helicopter briefly landed while the drone was intercepted before Netanyahu continued on his way.
Netanyahu repeatedly has warned that Hezbollah might try to take advantage of the instability in neighboring Syria, a key Hezbollah ally, to obtain what he calls game-changing weapons.
Israel has all but confirmed that it carried out an airstrike in Syria early this year that destroyed a shipment of sophisticated anti-aircraft missiles bound for Hezbollah.
A senior Lebanese security official, who also spoke on condition of anonymity in line with regulations, said Lebanon had no information on Thursday's incident.
Hezbollah spokesman Ibrahim Moussawi also said he had no information, adding the group would put out a statement if it had something to say on the issue.
When Israeli military shot down a Hezbollah drone on Oct. 6, it took days for Hezbollah leader Sheik Hassan Nasrallah to confirm it in a speech. He warned at the time that it would not be the last such operation by the group. He said the sophisticated aircraft was made in Iran and assembled by Hezbollah.