Israel has scrambled fighter jets to intercept a drone that crossed deep into Israeli airspace from the Mediterranean Sea, shooting the aircraft down over the country's southern desert.
The incident marked the first time in at least six years that a hostile aircraft has penetrated Israel's airspace.
Israeli officials said they were taking the incident seriously, raising the possibility of retaliatory action.
It was not immediately clear who launched the drone, but suspicion quickly fell on the Lebanese Islamic militant group Hezbollah.
The Iranian-backed group is known to have sent drones into Israeli airspace on several previous occasions.
Tensions are running high between Iran and Israel over Tehran's nuclear program, which the West believes is cover for the development of atomic weapons.
Iran denies the allegations, and says its programme is for peaceful purposes only.
Israel has threatened to carry out a military strike against Iran's nuclear facilities to prevent the Islamic republic from acquiring such weapons.
Lt Col Avital Leibovich said Israeli ground systems detected the drone, which flew over the Gaza Strip but did not originate there, yesterday morning.
They alerted the air force, which scrambled the jets to intercept the aircraft. She said Israel was still trying to determine where the drone took off from. Nobody was hurt in the incident.
Ms Leibovich said Israeli jets escorted the drone before deciding to bring it down in the northern Negev area, which is largely uninhabited.
The drone, which was downed near the Yatir Forrest close to the West Bank, had spent about 20 minutes in Israeli air space, an Israeli military official said on condition of anonymity in line with protocol.
Ms Leibovich did not give more details, but Israel media reported that the aircraft was not carrying explosives and could have been a surveillance drone.