An Israeli navy ship and an Israeli air force helicopter search for wreckage from a downed drone in the Mediterranean Sea. (Ariel Schalit/AP)

An unmanned aircraft that was approaching Israel on Thursday from the coast of Lebanon was shot down by an Israeli fighter jet over the Mediterranean Sea, about six miles from the northern Israel port of Haifa.

It was the second time in the past seven months that Israeli airspace was penetrated by a drone. A senior government official, who spoke on the condition of anonymity because the incident is under investigation, described it as a serious breach, saying such unmanned aircraft are intended to search for possible targets, probe defenses or create a provocation.

Suspicions immediately turned to the Lebanese political and militant organization Hezbollah, which asserted responsibility for a drone that flew over Israeli territory in October and was also shot down by Israel.

In an announcement broadcast on its television channel, Hezbollah denied involvement with the drone intercepted Thursday.

Israeli officials said it remained unclear who was remotely piloting the aircraft.

“We’re still looking into the source,” said Lt. Col. Peter Lerner, a spokesman for the Israeli Defense Forces. “We can say that it flew north to south, down the coast of Lebanon, and that we tracked it for about an hour with ground and aerial surveillance.”

An Israeli F-16 was scrambled and fired a missile at the drone, which was flying at about 6,000 feet. The military spokesman said the Israeli navy is searching for debris in the sea.

“I view with utmost gravity this attempt to violate our border,” Israeli Prime Minister Benjamin Netanyahu said.

The incident comes at a time of heightened tensions in the region, as neighboring Syria is engulfed in civil war.

“This could have been a way for Hezbollah to remind everyone that Israel is its main enemy and it wants to make this clear with such an act,” said Jonathan Spyer, an expert on Lebanon and Syria at the Global Research in International Affairs Center in Herzliya, Israel.

Analysts said that if Hezbollah was the source, the group probably assumed that the unmanned aircraft would be shot down but may have considered the flight a symbolic victory.

Hezbollah has been accused recently, inside and outside the Arab world, of sending fighters into Syria to support the regime of President Bashar al-Assad, which Israel fears may be funneling sophisticated weaponry to the group.

“Now Hezbollah is stretching its wings figuratively and showing everyone they have capabilities,” said Miri Eisen, a retired senior Israeli military intelligence officer. “It is Hezbollah showing they are still one of the key players in the region.”

The Israeli newspaper Haaretz reported Thursday that the chief of staff of the Israeli Defense Forces, Lt. Gen. Benny Gantz, said at a conference last month that Hezbollah has “a significant number of unmanned aerial vehicles, one of which has entered Israeli territory, a scenario we may encounter in the future.”

Ruth Eglash contributed to this report.