Incident comes four days after Hezbollah announced it had brought down an Israeli drone flying over the Blue Line.
Israel said it carried out air attacks on Hezbollah observation posts in Lebanon on Wednesday after shots were fired from across the border towards its troops the previous evening.
The country’s military had said earlier that a “security incident” was unfolding in the vicinity of Manara near the UN-demarcated Blue Line border between the two nations.
“During operational activity in northern Israel last night, shots were fired from Lebanon toward IDF troops,” the Israeli army wrote on Twitter.
“We responded with fire, & our aircraft struck Hezbollah observation posts near the border. This is a severe event & we remain ready to combat any threat to our borders.”
No Israeli soldiers were wounded in the firing, the military added.
Soldiers deployed illumination flares, smoke shells and live fire after the shots from the Lebanese side of the frontier, it said.
There was no immediate comment from Hezbollah.
Israel and Lebanon are still technically at war, and United Nations force UNIFIL is tasked with monitoring the ceasefire.
Hours earlier, Lebanon had rejected an Israeli call to reform a UN peacekeeping force patrolling the border ahead of a UN Security Council vote to renew its mandate.
The incident also comes after Hezbollah announced on Saturday that it had brought down an Israeli drone flying over the Blue Line.
Last September, Hezbollah vowed to shoot down Israeli drones flying over Lebanon, following an incident a month earlier when two drones packed with explosives targeted the group’s stronghold in south Beirut.
Last month, Israel said Hezbollah carried out an infiltration attempt, which the Iran-backed group denied.
Set up in 1978, UNIFIL was beefed up after a month-long devastating war in 2006 between Israel and Hezbollah.
The 10,500-strong force, in coordination with the Lebanese army, is tasked with monitoring a ceasefire and Israeli pullout from a demilitarised zone on the border.
Israel accuses Hezbollah of stockpiling weapons at the border to prepare for a new war.