Israel says one of its fighter jets has shot down an unmanned aircraft sent from Lebanon into Israeli airspace.
A missile brought down the drone about five miles (8km) west of the northern Israeli port of Haifa around 14:00 (11:00 GMT), officials said.
Reports suggest the drone could have been sent by Lebanese militant group Hezbollah, which fought a month-long war against Israel in 2006.
But Hezbollah later denied it had been behind the flight.
It is the second time in seven months Israel has downed a drone from Lebanon.
Last October, the Israeli air force shot down an unmanned aircraft over the south of the country.
Israeli Prime Minister Benjamin Netanyahu condemned the incident as an "extremely grave" attempt to breach Israel's borders.
"We will continue to do whatever it takes to protect the security of Israel's citizens," he said.
Mr Netanyahu was on his way to the north of Israel in a helicopter when the incident happened. His aircraft landed briefly until the Lebanese plane was shot down.
He recently warned that Hezbollah might try to take advantage of the instability in neighbouring Syria.
Israel says the latest aircraft was detected and monitored while still over Lebanon, and it was shot down by an air-to-air missile fired from an Israeli F-16 fighter jet, at an altitude of about 6,000ft (1,800 m).
"UAVs [unmanned aerial vehicles] pose a serious threat to the state of Israel's security," said an IDF report on the incident. "The IDF will not tolerate any attempt to violate Israel's sovereignty or harm its security."
Israel's Channel 2 television station reported that the aircraft took off from near Sidon in southern Lebanon and was quickly detected by Israeli air defence units, with warplanes and fighter helicopters dispatched to confirm it was not a civilian aircraft.
The commander of Israel's air force was following the incident from the control room and - once it had been established the drone was a hostile aircraft - ordered it to be shot down, the station reported.
Israeli ships are attempting to recover the remains of the drone from the sea, to try and determine if it was meant to explode over an Israeli target or simply take pictures.