Most Palestinian refugees living in camps in southern Lebanon or near Beirut have fled following escalating Israeli strikes, the head of the United Nations agency on Palestine refugees said on Friday, drawing parallels with mass displacement in Gaza.

UNRWA chief Philippe Lazzarini told Reuters that the agency continued to provide services to the most vulnerable left behind - and that repeatedly fleeing was sadly "part of the history" of Palestinians.

"Now, that's part, unfortunately, of the plight, but if you compare with what happened also in Gaza recently, you might have heard me describing how people are constantly being moved like pinballs. And one of the fears is that we replicate a situation similar to the one we have seen until now in Gaza," he said.

Israel has ramped up strikes across southern Lebanon and on Beirut's once-densely populated southern suburbs over the last three weeks, issuing evacuation warnings for more than 100 towns in southern Lebanon and neighbourhoods near the capital.

They include evacuation warnings and strikes on the Burj al-Barajneh Palestinian refugee camp in Beirut's southern suburbs and Rashidiyeh Palestinian refugee camp near the southern coastal city of Tyre.

Many of the Palestinians who arrived in Lebanon after Israel's creation in 1948, and their descendants, were living in 12 refugee camps around the country, which hosted about 174,000 Palestinian refugees.

Around 1.2 million people have been displaced in Lebanon and more than 2,100 people killed in the last year, most of them since Sept. 23, according to Lebanese authorities.

Hezbollah began launching rockets at Israeli military posts last October in solidarity with its ally, Palestinian group Hamas, which had carried out a deadly-cross border attack into Israel in which 1,200 people were killed and about 250 people were taken hostage, according to Israeli tallies.