Residents of the northern Israel town of Kiryat Shmona awoke to two large explosions. Israeli police spokesman Micky Rosenfeld said the rocket fire caused no injuries or damage. Shortly after, the Israeli military said it responded with artillery fired toward the source of the launch.
Lebanon's state news agency said the border area was shelled after the rockets hit Israel. The agency said more than 20 shells hit the mountainous region around the southern Lebanese border area of Rachaya.
Israeli Prime Minister Benjamin Netanyahu commended the military for responding "quickly and forcefully" to the rocket attack. He accused the government ofLebanon of "not lifting a finger" to stop the "war crimes" committed in its territory by Hezbollah guerrillas.
Defense Minister Moshe Yaalon said Israel "would not tolerate" such attacks and held the government and army of Lebanon responsible for any fire emerging from its territory.
"We will not allow incidents such as those of this morning to pass quietly," he said in a statement. "I would not recommend to anyone to test our patience and our determination to protect the security of the people of Israel."
The Israel-Lebanon border has remained mostly quiet since a monthlong war in the summer of 2006 between Israel and Hezbollah guerrillas in Lebanon. There have been sporadic outbursts of violence, most recently earlier this month when a Lebanese army sniper killed an Israeli soldier.
In the most serious incident, Lebanese forces killed a high-ranking Israeli officer in 2010 and Israel responded with artillery fire that killed three Lebanese. However, incidences of rocket fire have been infrequent since the countries agreed to a cease-fire that ended the 2006 war. The last such case took place four months ago.
The 2006 war broke out after Iranian-backed Hezbollah guerrillas crossed into Israel and captured two Israeli soldiers. The ensuing conflict killed about 1,200 Lebanese and 160 Israelis before ending in a United Nations-brokered cease-fire.
The U.N. peacekeeping force UNIFIL said its commander, Maj. Gen. Paolo Serra, made contact with the Israeli and Lebanese armies immediately after Sunday's incident and urged both sides to exercise "maximum restraint." He said UNIFIL had stepped up patrols in southern Lebanon to prevent any further incidents.
"I have been assured by the parties of their full cooperation with UNIFIL in this effort and of their continued commitment to the cessation of hostilities," Serra said in a statement. "It is of paramount importance to identify and apprehend the perpetrators of this attack and we will spare no efforts to this end working in cooperation with the Lebanese Armed Forces."
Israel and Lebanon have fought several wars before. In 1982, Israel invaded Lebanon with the stated intention of driving Palestinian guerrillas out of the south. The Israeli military battled halfway through the country into Beirut and occupied south Lebanon until 2000.
Given the years of enmity between the two countries, even the smallest incident raises the risk of sparking a wider conflagration.
Lebanon is unusually jittery after a Friday car bombing in an upscale district of Beirut. On Sunday, Lebanese soldiers fanned out throughout the country, manning checkpoints and closing off sensitive roads.
However, the Lebanese government remains unable to secure itself. Hezbollah has its own large, well-trained militia that dominates the southern border. There are also small bands of Palestinian militants who claim responsibility for some isolated rocket attacks.
No group immediately claimed responsibility for Sunday's rocket attack.
Aviv Oreg, a former Israeli military intelligence officer, said the incident was to be expected given the large number of "lone wolves" operating in Lebanonwithout any central control. He said it would likely be contained because the major players don't want matters to deteriorate at this time.
"At this stage, both Hezbollah and Israel have no interest in heating up the front and getting into a violent confrontation," Oreg said. "Hezbollah is deeply involved in the Syrian civil war and it is not focused on this front."
Associated Press writer Diaa Hadid in Beirut contributed to this report.