BEIRUT —  The Lebanese Hezbollah movement on Tuesday said a drone that crashed in its Beirut stronghold at the weekend contained an explosive device weighing more than five kilogrammes (11 pounds).

The Iran-backed Shiite group had previously said an Israeli reconnaissance drone had flown over the south of Beirut before crashing, and that a second armed drone had then "hit a specific area" before dawn on Sunday.

But after the party's "experts dismantled the first drone that crashed in Beirut's southern suburbs, it was found that it contained a sealed explosive device" of around 5.5 kilogrammes, it said in a statement.

"We confirm that the purpose of this first drone was not reconnaissance but the carrying out of a bombing attack," it added.

The latest discovery, Hezbollah said, confirms that Sunday's drone attack involved not one but two explosive-rigged drones -- one which exploded and the other that did not because of a technical failure.

Earlier on Monday, Lebanese President Michel Aoun denounced the Israeli drone attack as a "declaration of war".

It marked the first such "hostile action" in Lebanon since a 2006 war between Hezbollah and Israel, the party's chief Hassan Nasrallah said on Sunday, vowing retaliation.

Israel did not claim responsibility for the attack. But Prime Minister Benjamin Netanyahu said on Monday that his country was ready to use "all means necessary" to defend itself against Iranian threats "on several fronts".

The United Nations, meanwhile, has called for "maximum restraint" by all parties.

Hezbollah, considered a terrorist organisation by Israel and the US, is a major political actor in Lebanon and also a key government backer in war-torn Syria.

The reported Beirut drone attack came after Israel on Saturday launched strikes in neighbouring Syria to prevent what it said was an Iranian attack on the Jewish state.

Nasrallah on Sunday said two Hezbollah members were among those killed in the strike. They were laid to rest in Beirut's southern suburbs on Monday, amid a large turnout of party supporters. — AFP