Lebanese media reported that the IDF promptly retaliated, attacking targets in south Lebanon, but the army denied those reports.

An Israeli Iron Dome battery intercepted one of the rockets. Israeli TV aired footage of minor damage caused by a fragment from the rocket that fell on the outskirts of a town outside Nahariya. Another rocket fell in a town near Acre, causing damage to several houses.

Three residents were treated for shock.

Lebanese media reported that two volleys of rockets had been fired from a Palestinian refugee camp near the Lebanese town of Tyre. There was an attempt to fire a third volley, but the missiles fell short of the border.The IDF said four makeshift rocket launchers had been located east of Tyre.

The Abdullah Azzam Brigades, an al-Qaeda-inspired group based in Lebanon, claimed responsibility for the attack in a post on the Twitter account of Sirajuddin Zurayqat, a prominent Islamic militant leader. Zurayqat said the rockets were capable of flying 40 kilometers, or 25 miles, putting the Israeli city of Haifa in its range. The group, designated a terrorist organization by the US, has claimed responsibility for past rocket attacks on Israel.

The official Lebanese news agency reported Israeli unmanned aerial vehicles circling in the area, while a Hezbollah-affiliated station said IAF jets were executing sorties throughout the south of the country.

IDF sources said they regarded the incident — a little after 4 p.m. — as a one-off attack by a jihadist group rather than the beginning of a wider campaign. Northern residents were initially told to go to bomb shelters; the army later called on them to remain close to the shelters but otherwise go back to their normal routines.

The specific location of the rocket falls was not publicized, by order of the military censor, in order to avoid assisting cells firing rockets at Israel in hitting targets in future attacks.

A resident of Kibbutz Evron, near Nahariya, told Ynet that the alarm sounded after “two booms” were heard, and that the residents quickly moved into bomb shelters.

“I heard booms,” Yan, a resident of Nahariya, told Channel 2. “Everyone is in the bomb shelters.”

He said that residents hadn’t heard alarms for seven years — since the 2006 Second Lebanon War.

“I was on the phone to my grandma” when the alarms rang out. “I put down the phone and went down to the shelter,” Yan said.

Prime Minister Benjamin Netanyahu said the army was “employing diverse means, both defensive and preemptive measures,” in order to ensure Israelis’ security. “Anyone who harms us, who tries to harm us, should know that we will harm them,” Netanyahu said in a videotaped statement.

There were reports Wednesday in Lebanon that Israeli helicopters had circled in the south of the country.

There were several reports in the past year of attempts to fire rocketsinto Israel from southern Lebanon. In November, during Israel’s brief round of fighting with Hamas in Gaza, Lebanese army forces operating in the town of Marjayoun, about 10 kilometers north of the border, found and disarmed several rockets aimed at Israel.

Rockets are a key tactic of the Lebanese Hezbollah and other terror groups on Israel’s northern and southern borders.

Thousands of projectiles fell on Israel during the Second Lebanon War in the summer of 2006, and Hezbollah has since stockpiled tens of thousands of rockets it has said will be launched at Israeli cities in future fighting.

Israel last week deployed a sixth Iron Dome battery north of Tel Aviv, with an eye to the missile threat from the north.

The anti-missile system is a keystone of Israel’s air defense array and successfully intercepted hundreds of short- and medium-range missiles shot at Israeli cities during the conflagration in Gaza in November.

The Associated Press contributed to this report.