Lebanon's President Michel Aoun said on Monday that two Israeli drone incursions into Lebanese territory were a "declaration of war".
Two drones crashed early on Sunday in southern Beirut in strongholds of the Lebanese Shiite militia Hezbollah.
He said that the country had a right to defend its territory.
"What happened was similar to a declaration of war which allows us to resort to our right to defending our sovereignty," Mr Aoun's office quoted him as saying on Twitter.
"We are a people who want peace, not war, and we don't accept anyone threatening us in any way," he added, according to a statement from the presidency.
The drone incursions prompting the Iran-backed movement Hezbollah to warn Israeli soldiers at the border to await a response.
His office said that he discussed on Monday the "Israeli assault on the southern suburbs of Beirut" with the country's United Nations Special Coordinator.
Mr Aoun met UN Special Coordinator for Lebanon Jan Kubis on Monday to discuss "the latest developments", the president's office said on Twitter.
Separately, Prime Minister Saad Hariri met Lebanon's interior and defence ministers and with the army chief on Monday to discuss security issues, his office said, though it gave no further details.
Mr Hariri, who has said the drones aimed to stir up regional tensions, is also due to meet the ambassadors of the U.N. Security Council's five permanent members, his office said.
Israeli drone strikes hit a military position belonging to a Palestinian faction in Lebanon's Bekaa valley early on Monday, the group said.
Although Israel has not claimed the Beirut attack, Hezbollah leader Hassan Nasrallah said it was the first Israeli attack inside Lebanon since the two sides fought a deadly month-long war in 2006.