UNIFIL, the United Nations monitoring force on the border between Israel and Lebanon, urged both sides to "exercise maximum restraint" following clashes on Sunday, according to AFP.
"This is a very serious incident... and is clearly directed at undermining stability in the area," UNIFIL chief Paolo Serra said in a statement. "UNIFIL's first imperative is to ensure that there is no further escalation of the situation."
Lebanese army and UNIFIL forces were carrying out patrols in the area after the exchange of fire, an AFP correspondent said.
5 rockets were fired at Israel Sunday morning, but only one hit Israeli soil. The rocket hit an open field near the city of Kiryat Shmona; no injuries were reported. In response, the IDF shelled targets in Lebanon, aiming to eliminate the source of the rocket fire.
It is unclear who fired the rockets, though both Palestinian terrorist groups in Lebanon and Hezbollah have been suspected to be the culprit. Both the IDF and Defense Minister Moshe Yaalon warned Lebanon to monitor its own citizens carefully following the attack.
"We will not tolerate firing at us from Lebanon, or to allow a threat of any kind on the lives of Israeli citizens," Yaalon warned.
"We see the government of Lebanon and the Lebanese army as responsible for the rocket fire shooting this morning and what happens in their territory, and what happened this morning will not be overlooked."
"The IDF responded by firing, a short while ago, massive shells into the launching area," Yaalon continued. "If necessary we will act more forcefully. I would not recommend anyone to test our patience and our determination to protect the security of Israeli citizens."
Earlier this month, tensions rose between Israel and Lebanon after a Lebanese army soldier shot and killed 31 year-old IDF Master Sergeant Shlomi Cohen. The attacker eventually turned himself in to Lebanese authorities, and will beplaced on trial there over the incident, according to Yaalon.