JERUSALEM (AFP) - The Israeli air force said it carried out its first air strikes on neighbouring Lebanon in seven years on Thursday (Aug 5), following a second day of rocket fire across the border.

"Earlier today (Thursday), rockets were fired from Lebanon into Israeli territory," the air force tweeted.

"In response... fighter jets struck the launch sites and infrastructure used for terror in Lebanon from which the rockets were launched.

"An additional target in the area from which rockets have been launched in the past was struck as well."

Israeli aircraft routinely strike Palestinian militant targets in Gaza and suspected Hezbollah or Iranian targets in Syria but it was the first time since 2014 that they had hit targets in Lebanon, the air force confirmed.

Lebanon's Al-Manar television, run by powerful Shi'ite militant group Hezbollah, said Israeli aircraft carried out two strikes at around 12.40am outside the town of Mahmudiya, about 11km from the border.

Lebanon's official National News Agency also reported the strikes but provided few details.

Lebanese President Michel Aoun said "Israel's use of its air force to target Lebanese villages is the first of its kind since 2006, and suggests an intention to escalate attacks" against Lebanon.

Israeli warplanes last struck Lebanese territory near the border with Syria in 2014, but they have not targeted Hezbollah's south Lebanon strongholds since the militants fought a devastating conflict with Israel in 2006.

Thursday was the second straight day that Israel had reported rocket fire from Lebanon.

Three rockets were fired on Wednesday, two of which reached Israel, striking near the northern town of Kiryat Shmona, where four people were treated for "stress symptoms".

In response to that attack, the Israeli army carried out three rounds of retaliatory shelling of south Lebanon.

It triggered multiple brush fires in the tinder-dry conditions but there were no reports of casualties.

The Lebanese army said 92 artillery shells fired by Israel landed in southern Lebanon following the Wednesday rocket fire.

It said it was investigating who fired the rockets.

The exchange came as thousands of grief-stricken Lebanese marked the first anniversary of a devastating explosion in Beirut port that killed at least 214 people and irreparably scarred the nation's psyche.

The then government resigned in the face of a wave of popular anger but a year later, despite a worsening economic meltdown, no replacement administration has been formed.

Israel has warned repeatedly that it will not allow the power vacuum in Beirut to undermine security on its northern border.

The military said it "views the state of Lebanon as responsible for all actions originating in its territory, and warns against further attempts to harm Israeli civilians and Israel's sovereignty".

The United Nations peacekeeping force Unifil, which has been deployed in Lebanon since 1978 and has patrolled the border since a devastating conflict between Israeli and Hezbollah in 2006, called for restraint from all sides.

"Unifil's head of mission and force commander, Major General Stefano Del Col, was in immediate contact with the parties," the force said in a statement on Wednesday.

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

"It is imperative to restore stability immediately so Unifil can begin its investigation."