A drone flown by Lebanese militant group Hezbollah crossed into northern Israel on Friday, triggering air defenses and the scrambling of fighter jets.

The drone apparently returned to Lebanon but it is not clear how long it lingered in Israeli airspace (video).

Iran-backed Hezbollah, which fought a month-long war against Israel on the Lebanon border in 2006, said Friday's flight was a 40-minute reconnaissance mission. Earlier this week, it said it had started producing its own drones in Lebanon.

Hours later and roughly 100 km to the north, a thundering roar was heard in the Lebanese capital Beirut caused by Israeli planes passing in the lowest overflight in years, according to many videos recorded by residents.

On Wednesday, Hezbollah chief Hassan Nasrallah said in a televised speech that his group has the ability to convert rockets into precision missiles with the help of "experts from the Islamic Republic."

Israel's military said Hezbollah's radio-controlled drone had set off air raid sirens in the Galilee region of northern Israel warning residents to take cover.

"Aerial defense systems identified and tracked the threat along with helicopters and fighter jets that were dispatched," it said, adding that its Iron Dome defense system had tried to intercept the drone but it made it back.

On Thursday, Israel said it had downed a drone that belonged to Hezbollah after it crossed into Israeli air space.

With reporting by Reuters