Hezbollah leader Hassan Nasrallah said his group would bring down any Israeli drone that breached Lebanese airspace, after a drone damaged the group’s media office in south Beirut, injuring three people.
Two drones came down in southern Beirut, but only one of them exploded, damaging the Hezbollah office, report said.
In an impassioned speech, Nasrallah said the Israeli drone attack was the first since Hezbollah fought a month-long war with Israel in 2006. He described it as “very, very dangerous”.
From now on, the group would “face Israeli drones in the skies of Lebanon and bring them down”.
Banging his fist on the table, Nasrallah repeated that “what happened last night will not pass”.
Hezbollah has been called a terrorist group by the US but operates like a normal party in Lebanon and has three ministers in the current government.
The Iran-backed group also controls one of the region’s most powerful militias, which it kept in the name of the fight against Israel when the country’s civil war ended in 1990.
Nasrallah was giving a commemorative on the second anniversary of an operation with the Lebanese army to rid north-east Lebanon of extremists from ISIS and Jabhat Al Nusra.
As he spoke, another drone strike hit an Iran-backed paramilitary force operating on the Syria-Iraq border.
On Saturday night, Israel admitted it had launched a pre-emptive attack against an Iranian base near the Syrian capital Damascus to thwart a drone strike.
But Nasrallah said that Israel had actually aimed at Hezbollah and killed two of its fighters.
“If Israel kills any of our brothers in Syria, we will respond in Lebanon,” he said.
The Lebanese state-run National News Agency reported that its army had intensified patrols along the blue line, the UN-monitored border between Israel and Lebanon.
It said that Israeli planes were flying lower than usual above the south of the country.
Nasrallah accused Israeli Prime Minister Benyamin Netanyahu of orchestrating the attacks to gain popularity before the September legislative elections.
“Netanyahu is preparing his elections with your blood," he told the audience.
In the middle of the night on Saturday, local youths living in Beirut’s Southern suburb of Dahieh, a Hezbollah stronghold, saw a drone two metres long and brought it down by throwing stones, Nasrallah said.
A second drone laden with explosives then appeared and exploded at 2.30am local time near Hezbollah's media office, shattering windows and slightly injuring three journalists.
The party allowed journalists to inspect the damage early on Sunday afternoon. Plaster had fallen off the ceiling on the stairs and was lying by the entrance of the media office.
Office tables – with pictures had been stuck of Nasrallah, supreme leader Ayatollah Ali Khamenei and his predecessor Ruhollah Khomeini – were covered in glass.
Mohamed Afif, head of Hezbollah’s media office, said that the second drone had exploded between four and 10 metres above ground. Another official said it was carrying four kilograms of explosives.
Mr Afif said that the drone fell, not that it was shot down, in a clear attempt to avoid accusations that Hezbollah was inflaming regional tension.
No Hezbollah leader officially pointed fingers at Israel until Nasrallah gave his speech in the early evening.
But the Lebanese army confirmed hours the drones were Israeli.
A fragile truce was brokered between Hezbollah and Israel after their latest confrontation in the summer of 2006.
On Sunday, Lebanese officials including President Michel Aoun and Prime Minister Saad Hariri condemned the drones' presence as clear breaches of Lebanon’s sovereignty and of the UN security resolution that ended the 2006 war.
The resolution banned all unauthorised weapons between the Litani River and the blue line.
The leaders said they would complain to the UN Security Council.
US Secretary of State Mike Pompeo called My Hariri on Sunday and stressed the need to avoid any escalation, the National News Agency reported.
Nasrallah acknowledged that “the Lebanese state’s condemnation of the attack or its complaints to the Security Council are good”.
But he shouted angrily that “we, as Hezbollah, completely reject this however much it costs”.
Hezbollah’s weapons are a hot topic of discussion in Lebanon.
After the drone attack, pro-Hezbollah Lebanese politicians argued that it was a clear indication that the country needed to keep them.
But political parties critical of the group’s military power called for Lebanese to unite around the state.
The drone attack on Hezbollah’s media centre is still under investigation, Mr Afif said.
“How it fell, and whether it was operated remotely or not, we do not know yet,” he said.