President Michel Aoun said Monday that Lebanon had a right to defend itself, likening Israeli drone strikes to a "declaration of war" amid rising tensions between the Iran-backed Hezbollah movement and Israel.
Israel's military said its northern command was on high alert at the borders with Syria and Lebanon, as Lebanon's Prime Minister Saad al-Hariri urged diplomats to help prevent an escalation.
After two drones crashed Sunday in Beirut's southern suburbs, which are dominated by Hezbollah, the heavily armed movement warned Israel to await a response.
In a Sunday speech, the leader of Hezbollah, Sayyed Hassan Nasrallah, issued the toughest threats to his enemy in years and said the drones had launched a "new phase."
While Israel has not claimed the Beirut drone attack, Nasrallah deemed it the first Israeli attack inside Lebanon since the two sides fought a deadly month-long war in 2006.
Only hours later, a Palestinian faction said Israeli drones had struck a military position it holds in Lebanon's Bekaa valley before dawn Monday.
"What happened was similar to a declaration of war which allows us to resort to our right to defending our sovereignty," the Lebanese president's office quoted Aoun, a political ally of Hezbollah, as saying Monday on Twitter. "We are a people seeking peace, not war, and we don't accept anyone threatening us in any war."
Aoun discussed the "Israeli assault" with the country's United Nations Special Coordinator Jan Kubis on Monday, the presidency said. He told Kubis the attacks in the Dahyeh suburbs and in the Bekaa violated U.N. Security Council Resolution 1701 that ended the July 2006 war.
Aoun and Hariri called for Lebanon's Higher Defense Council to meet Tuesday.
Hariri said his government wants to avoid a "dangerous escalation" of tensions with Israel. But this requires the international community rejecting Israel's "blatant violation," he told ambassadors from the U.N. Security Council's five permanent members.
The Western-backed Hariri, whose coalition cabinet includes Hezbollah, told the diplomats their countries must help to preserve stability in Lebanon. "Any escalation could develop into a regional cycle of violence that nobody can predict the extent of," he said.
Israeli Energy Minister Yuval Steinitz said his country remained vigilant about the possibility of a Hezbollah attack under orders from its regional arch-foe Iran.
"Undoubtedly, the situation is tense. One does not know what a new day will bring," Steinitz, a member of Prime Minister Benjamin Netanyahu's security cabinet, said in a video interview with Israel's YNet news website.
U.S. Vice President Mike Pence said he spoke on Monday with Israeli Prime Minister Benjamin Netanyahu and reiterated U.S. support for Israel.
Also at the weekend, Israeli airstrikes killed two Lebanese Hezbollah fighters in Syria, where Hezbollah and Tehran are providing military support to Damascus.
Israel, alarmed by Tehran's rising influence in Syria, says its air force has struck what it deems Iranian targets or Hezbollah arms transfers hundreds of times.
Netanyahu has hinted at possible Israeli involvement in attacks against Iran-linked targets in Iraq too.
Nasrallah pledged on Sunday that his fighters would prevent such attacks from happening in Lebanon at any cost.
The 2006 war killed nearly 1,200 people, mostly civilians, in Lebanon and 158 people in Israel, mostly soldiers.
U.N. Resolution 1701, which halted the war, banned all unauthorized weapons between the Litani River in south Lebanon and the U.N.-monitored border between Israel and Lebanon.