"The humanitarian crisis in Lebanon is severe and deteriorating," the UN humanitarian agency OCHA said in a revised appeal for the country.

"Repeated displacements, insufficient shelter capacity and limited prospects for safe return are deepening vulnerability," it said, warning that "affected people are rapidly exhausting their coping capacities, and essential services are under increasing strain".

The UN had appealed for $308 million in March to support a massive emergency response led by Lebanon's government through to the end of May.

On Friday it said that another $331 million would be needed through the end of August.

Only $185 million had so far been received out of the initial appeal, OCHA said, adding that that amount had helped provide assistance to around 680,000 people between March 2 and May 31.

The aim now, it said, was to more than double that number to reach all of the 1.4 million people in Lebanon -- around a quarter of the population -- estimated to need humanitarian assistance in the country.

Lebanon says Israeli attacks have killed more than 3,500 people since Hezbollah drew Lebanon into the wider Middle East war on March 2, firing rockets at Israel in retaliation for US-Israeli strikes that killed Iran's supreme leader.

Nearly one million people have fled their homes while more than 1.2 million are facing acute food insecurity, Friday's appeal showed.

Price pressure was adding to the misery, with the cost of water, fuel and electricity up more than a third nationally, and as high as 70 percent in the conflict-affected areas, it said.

It also highlighted the strain that the conflict was placing on healthcare in Lebanon, with 62 hospitals and other health facilities either damaged or closed.

OCHA said nearly 450 schools were being used to shelter displaced people, driving learning loss and drop-out risks.