Israel's launched its "David's Sling" air defence system for its first ever operational mission on Monday as a precauation against rockets fired within neighboring Syria, setting off sirens in northern Israeli communities, the IDF said.

The rockets fell inside Syrian territory and were part of internal fighting, a military statement said. It did not elaborate on whether whether they had been shot down by the two interceptors launched by David's Sling, a mid-range Israeli system jointly manufactured by US firm Raytheon.

David's Sling goes into action in northern Israel (צילום: אדיר זאדה)

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A number of Code Red alert sirens were blasted across northern Israel, triggering the launch by the David's Sling system, which was originally reported to be a Patriot missile.

A first wave of alerts was sounded at 10:04 in Safed, Katzrin, the Merom HaGalil Regional Council, the upper Galilee, the Golan Regional Council and the Mevo'ot HaHermon Regional Council.

They were followed by a second wave of sirens mere minutes later in the same locations, while Israeli fighter jets circled the area during the incident.

Israel has been on high alert as Syrian President Bashar Assad's Russian-backed army advances against southern rebels, bringing it close to the Israeli side of the Golan Heights.

Israeli leaders have said they worry that Assad may try to defy a 1974 demilitarization deal on the Golan or allow his Iranian and Lebanese Hezbollah allies to deploy there.

Within half an hour of the first siren, the Katzrin Council announced that residents could resume their daily business. Only one siren was sounded in Katzrin and residents were asked to stay alert.

In Safed, authorities began opening bomb shelters in a local effort to calm the city's residents.

David's Sling missile launched in Safed (Photo: Adir Zadah)

Ten days ago, Israel fired a Patriot missile at a UAV approaching its border from Syria, making it the second such an incident in one week.

The Patriot was launched from Safed and a witness on the Syrian side of the frontier said the drone had been brought down.

"A Patriot missile of the IDF's (Israel Defense Forces) aerial defense system was launched towards a Syrian UAV flying over the demilitarized zone. The UAV was most likely intercepted," the military said in a statement.

The army said the drone was intercepted over the buffer zone between the two countries.

The IDF said it will "operate against attempts to violate the 1974 Separation of Forces Agreement, threats to Israeli sovereignty and any attempt to harm Israeli civilians."

On Sunday evening, the Syrian news agency SANA reported that an Israeli air strike had hit a military post in the city of Misyaf in Syria's Hama province.

The Hezbollah-affiliated Al Mayadeen network reported that the alleged targets were scientific research centers for chemical arms production.

A Syrian military source said that "one of the military sites near Misyaf was attacked by the Israeli Air Force (IAF)," according to the SANA news agency.

The source added that only damage to property was caused, and no casualties were immediately reported.

However, Syrian opposition members reported that Iran's Revolutionary Guards as well as Hezbollah's members were killed in the alleged the strike.