Two rockets launched from Lebanon on Wednesday struck Israel, which responded with artillery fire, amid heightened regional tensions over an alleged Iranian attack on an oil tanker in the Gulf last week.

Israel's Magen David Adom national ambulance service said there were no casualties on the Israeli side of the hilly frontier, where the rockets ignited a brush fire.

There was no immediate claim of responsibility for the rocket strike, launched from an area of south Lebanon under the sway of Iranian-backed Hezbollah guerrillas.

Sirens warning of a rocket attack sounded in several Israeli communities, including the northern town of Kiryat Shmona, near the Lebanese border.

In a statement, Israel's military said three rockets were launched from Lebanon, with one falling short of the Israeli border and the others striking inside Israel. Witnesses in Lebanon also reported that several rockets were fired at Israel.

"In response, [Israeli] artillery forces attacked Lebanese territory," the military said. Some two hours after the initial shelling, the military said its artillery had fired again at targets, which it did not identify, along the frontier.

The United Nations Interim Force in Lebanon said its Head of Mission and Force Commander, Major General Stefano Del Col, was in contact with both parties.

"He urged them to cease fire and to exercise maximum restraint to avoid further escalation, especially on this solemn anniversary," the statement said.

The border has been mostly quiet since Israel fought a 2006 war against Hezbollah, which has advanced rockets.

But small Palestinian factions in Lebanon have fired sporadically on Israel in the past, and two rockets were launched at Israel on July 20, causing no damage or injuries. Israel responded to that incident with artillery fire.

The latest border incidents occurred after an attack last Thursday, which Israel blamed on Iran, on a tanker off the coast of Oman. Two crew members, a Briton and a Romanian, were killed. Iran has denied any involvement.

On Tuesday, Britain, Romania and Liberia told the United Nations Security Council it was "highly likely" that Iran used one or more drones to strike the Mercer Street — a Liberian-flagged, Japanese-owned petroleum product vessel managed by Israeli-owned Zodiac Maritime.

The United States and Britain said on Sunday they would work with their allies to respond to the attack. Israeli Prime Minister Naftali Bennett said on Tuesday that Israel was keeping open the option of acting alone against Iran if necessary.