JERUSALEM — In the first border flare-up of its kind in four months, at least one Katyusha rocket fired from Lebanon struck northern Israel on Sunday, triggering a heavy artillery barrage from Israeli forces in response. No casualties were reported on either side of the frontier.

Israeli Prime Minister Benjamin Netanyahu, in a harshly worded statement to his Cabinet, blamed the Shiite Muslim militia Hezbollah for the rocket strike and condemned the Lebanese army for failing to "lift a finger" to rein in the group.

The United Nations peacekeeping force in southern Lebanon urged restraint on both sides and said it was in contact with Israeli and Lebanese authorities.

It was not immediately clear who fired the rockets, at least one of which struck outside the Israeli border town of Kiryat Shmona. Residents reported loud explosions as the projectile landed in an open area west of the town.

Israel said it detected five rocket launches aimed in its direction. Lebanon's state-run National News Agency reported that at least two fell short of their intended targets, landing instead in Lebanese territory, about six miles from the market town of Marjayoun.

Israel fired back with an undisclosed number of artillery shells. The Lebanese news agency said at least 20 of them fell on several southern farming hamlets, but it reported no injuries or deaths.

Israel's military called the attack "inexcusable and blatant," and Defense Minister Moshe Yaalon reminded the Lebanese government that Israel holds it responsible for hostile actions originating in Lebanese territory.

Israel filed a complaint with the U.N. Interim Force in Lebanon.

Since the 34-day war between Israel and Hezbollah in 2006, the border has been largely quiet. The U.N., Lebanese authorities and Israel have all worked to prevent escalation of any incident.

Two weeks ago, an Israeli soldier was killed by shots fired over the border by a sniper from the Lebanese armed forces, and Israeli troops fired back, but hostilities went no further after indications that the shooting was a rogue assault.

The mayor of Kiryat Shmona, Nissim Malka, told reporters that residents had not been instructed to take any special security precautions, as they would have been advised to do in the event of a serious attack.

Sobelman is a news assistant in The Times' Jerusalem bureau. Special correspondent Nabih Bulos in Amman, Jordan, and Times staff writer Laura King in Cairo contributed to this report.