An Israeli fighter plane shot down a drone from Lebanon over the Mediterranean sea on Thursday as it was approaching the Israeli coast, the military said.
Lebanon's Hezbollah militant group, which sent a drone deep into Israel in October, said it was not behind the latest incident. Israel's military held back from accusing the group, saying an investigation was under way.
Prime Minister Benjamin Netanyahu said he was flying in a military helicopter to an event in northern Israel when the unmanned aircraft was spotted along the Lebanese coast by Israeli air defences. His helicopter landed briefly until the interception was completed.
There was no indication from Israeli officials who provided information about the incident that Israel suspected any connection between the dispatch of the drone and Netanyahu's flight, whose details had not been made public.
"I view with great gravity this attempt to violate our border. We will continue to do what is necessary to defend the security of Israel's citizens," Netanyahu said in a speech at his destination, a Druze village where he met community leaders.
There was no immediate claim of responsibility for the alleged aerial infiltration.
In a statement, Hezbollah denied sending "any surveillance plane towards the occupied Palestinian land".
Six months ago, a Hezbollah drone flew some 35 miles (55 km)into southern Israel before being shot down by an F-16.
Israel and Hezbollah fought a war in 2006, and Lebanon has complained to the United Nations about frequent Israeli overflights, apparently to monitor the group's activities.
The military said the drone shot down on Thursday was detected in Lebanese skies and intercepted by an F-16 fighter jet 5 nautical miles west of the Israeli port city of Haifa.
A military spokesman said the unmanned aircraft had been flying at an altitude of about 6,000 feet and had been monitored by Israel for about an hour before it was destroyed by an air-to-air missile.
"We don't know where the aircraft was coming from and we don't know where it was actually going," the spokesman said.
On Monday, Israeli Defence Minister Moshe Yaalon said Israel would not permit "sophisticated weapons" to fall into the hands of Hezbollah "or other rogue elements" in Syria's civil war.
"When they crossed this red line, we acted," Yaalon said at a news conference with U.S. Defense Secretary Chuck Hagel, in comments widely interpreted as confirming reports that an Israeli air strike in Syria in January had targeted a Hezbollah-bound arms convoy.