By Laila Bassam and James Mackenzie

BEIRUT/JERUSALEM (Reuters) -Israel on Friday carried out its first major airstrike on Beirut's southern suburbs in months, retaliating for an earlier rocket launch from Lebanon in the most serious test of a shaky ceasefire deal agreed in November.

The strike targeted a building in the southern suburbs of the Lebanese capital, a Hezbollah stronghold known as the Dahiyeh, that Israel said was a drone storage facility belonging to the Iranian-backed Shi'ite Muslim militant group.

The ceasefire has looked increasingly flimsy in recent weeks. Israel delayed a promised troop withdrawal in January and said last week it had intercepted rockets fired on March 22, which led it to bombard targets in southern Lebanon. Hezbollah has denied any involvement in the rocket firing.

Israel is also renewing its military campaign in Gaza after the collapse of a January ceasefire with Hamas - a resumption of major warfare that has set the wider region back on edge.

The south Beirut airstrike was heard across the Lebanese capital and produced a large column of black smoke. It followed an evacuation order by Israel's military for the neighbourhood, and three smaller targeted drone strikes on the building intended as warning shots, security sources told Reuters.

The evacuation directive sent residents of the area into a panic. They rushed to escape on foot as traffic clogged the streets out of the area, Reuters reporters in the area said.

Beirut's southern suburbs were pounded last year by Israeli airstrikes that killed many of Hezbollah's top leaders, including its powerful long-time chief Sayyed Hassan Nasrallah in a September air attack.

In south Lebanon, smoke rose from Israeli artillery strikes against targets in the hills just across the border.

The truce in November halted the fighting and mandated that southern Lebanon be free of Hezbollah fighters and weapons, that Lebanese troops deploy to the area and that Israeli ground troops withdraw from the zone. But each side accuses the other of not entirely living up to those terms.

Israeli Prime Minister Benjamin Netanyahu said on Friday Israel would continue to attack anywhere in Lebanon to counter threats and enforce the ceasefire accord.

"Whoever has not yet internalised the new situation in Lebanon, has (today) received an additional reminder of our determination," he said. "We will not allow firing at our communities, not even a trickle."

No group has claimed responsibility for the rocket fire. The Lebanese army said it was able to locate the launch site of Friday's rocket attacks and had begun an investigation to identify those responsible.

CRITICISM

Israeli ministers have vowed to ensure that the tens of thousands of Israelis who evacuated their homes in border areas when Hezbollah began bombarding the area in 2023 would be able to return safely.

But with more Israeli military units deployed around Gaza, where 19 Palestinians were killed in Israeli strikes on Friday, according to local health authorities, it remained unclear whether Israel was prepared for any wider intervention.

Hezbollah denied any role in the rocket fire on March 22 and on Friday. President Joseph Aoun said a Lebanese investigation into last week's attack did not point to Hezbollah and called Friday's strike on Beirut unjustified.

French President Emmanuel Macron, whose government helped mediate the ceasefire in November, criticised Israel for what he called "unacceptable strikes on Beirut" that he said did not respect the ceasefire and played into Hezbollah's hands.

"The Israeli army must withdraw as quickly as possible from the five positions it continues to occupy in Lebanese territory," he said, adding he would speak with both Israeli and U.S. leaders.

Israel's statement confirming its air raid on Dahiyeh said that the Friday morning rocket fire amounted to "a blatant violation of the understandings between Israel and Lebanon and a direct threat to the citizens of the State of Israel."

It added that the Lebanese state bears responsibility for upholding the agreement.

Israel has vowed a strong response to any threats to its security, stirring fears that last year's conflict - which displaced more than 1.3 million people in Lebanon and destroyed much of the country's south - could resume.

The United Nations Special Coordinator for Lebanon, Jeanine Hennis-Plasschaert, said the firing across the southern border on Friday was "deeply concerning."

"Any exchange of fire is one too many. A return to wider conflict in Lebanon would be devastating for civilians on both sides of the Blue Line and must be avoided at all costs," she said in a written statement.

(Reporting by Tala Ramadan, Jana Choukeir in Dubai; Maya Gebeily and Laila Bassam in Beirut, and James Mackenzie in Jerusalem; Writing by Tala Ramadan, Jana Choukeir and Angus McDowall; editing by Christian Schmollinger, Lincoln Feast, Timothy Heritage, William Maclean and Mark Heinrich)