Over the past two days, Lebanese authorities "recorded the crossing of 15,600 Syrian citizens and 16,130 Lebanese citizens into Syrian territory," a statement from the country's disaster management unit said.

Earlier on Thursday, Syrian security sources reported different figures, saying more than 22,000 people had crossed from Lebanon into Syria via two of the countries' border crossings this week.

According to the UN, Israel's bombardment of Lebanon has forced 90,000 people to flee their homes in southern Lebanon to safer areas elsewhere in the tiny Mediterranean country.

The mass displacement comes as Israel's military said it carried out fresh strikes on Thursday across the country and its capital, Beirut, despite a US-led call for a ceasefire.

Lebanon's health ministry said Thursday that 20 people, almost all Syrians, were killed in an overnight Israeli strike in east Lebanon, after the Israeli military claimed it hit Hezbollah targets in the area.

An "Israeli enemy strike on the village of Yunin" killed "20 people, including 19 Syrian nationals", the health ministry said in a statement, raising an earlier toll of nine dead.

Israeli fighter jets also struck infrastructure on the Syria-Lebanon border on Thursday as thousands were fleeing Israeli bombardment in Lebanon. The Israeli military repeated claims it was hitting Hezbollah sites.

Hezbollah said Thursday that it again targeted defence industry complexes in northern Israel near the city of Haifa.

"Defending Lebanon and its people", Hezbollah fighters "bombed the Rafael military industry complexes... with salvos of rockets", the group said in a statement, after announcing several previous targetings of the site since Sunday.

Human Rights Watch warned on Wednesday that Israeli strikes on Lebanon were putting civilians "at grave risk", urging an international investigation into hostilities in the country and in northern Israel.

Israeli strikes since Monday have killed more than 630 people in Lebanon, according to local health authorities, who say around a quarter were women and children. Several people have been wounded by shrapnel in Israel.

Israel struck 75 sites overnight across southern and eastern Lebanon, the military said. At least 45 projectiles were fired from Lebanon early Thursday, all of which were intercepted or fell in open areas, it said.

*This story was edited by Ahram Online.