"The Israeli enemy strike near the Hariri Hospital killed, in a preliminary toll, four people, including a child, and injured 24," the health ministry said, adding it had caused "significant damage to the hospital".

In a separate statement, the ministry said the strike hit the entrance to the hospital, "which is still operating and receives a large number of patients".

It denied claims by the Israeli army that Hezbollah had stored half a billion dollars under the Sahel hospital in south Beirut.

Lebanon's National News Agency reported at least three Israeli strikes on the Ouzai district of south Beirut.

While most districts of Beirut's southern suburbs had been emptied for almost a month, the densely-packed residential area of Ouzai was still filled with people because it had never been targeted before.

- 'No room for escape' -

The NNA reported more than a dozen strikes on various south Beirut districts including Haret Hreik, just south of Ouzai, and Hadath.

Hezbollah-affiliated rescuers told AFP they were looking for survivors amid the devastation in Ouzai, adding that the evacuation order, then the strike, caused "panic among residents" who "started to run in the streets".

"They did not leave any room for people to escape. The strike came closely after the warning," one said.

A Lebanese security official told AFP that the country's national airline had to switch landing strips after Israeli strikes near Beirut's only international airport hit close to the main runway.

"Middle East Airlines switched the runway it was using because the main runway is close to the site of the Ouzai strike," the official said, requesting anonymity to discuss sensitive matters.

AFPTV footage showed plumes of smoke rising from Beirut's southern suburbs, with AFP correspondents also hearing several loud bangs before the strikes.

The footage also showed two strikes that caused a huge fire, with black smoke surrounding dissipating orange flames.

Just prior to the strikes, the Israeli military called on residents to leave parts of southern Beirut, in their latest such appeal.

Military spokesman Avichay Adraee posted the new call on social media indicating several locations to be evacuated, including an area close to Beirut airport.

"You are located near facilities and interests affiliated with Hezbollah that the IDF will work against in the near future," he wrote.