Five Iran-backed fighters have been killed in a drone strike in Syria's east, near the Iraqi border, a war monitor said, adding it was not clear yet who was behind the attack.

"Five pro-Iranian fighters were killed and others were injured, some severely... after an unknown drone targeted the military vehicle they were in... near the Syrian-Iraqi border," said the Syrian Observatory for Human Rights.

Iraq's top Shiite Muslim cleric Grand Ayatollah Ali Sistani has warned of the risk of a regional escalation with potentially "catastrophic consequences" following the killing of two Iran-backed militant leaders.

Sistani also urged an end to the "genocidal war" in Gaza, where the civil defense agency said an Israeli air strike Saturday on a school housing displaced Palestinians killed more than 90 people.

The Israeli military ordered more evacuations in southern Gaza early Sunday after a deadly airstrike on a school-turned-shelter in the north killed at least 80 Palestinians, according to local health authorities. Israel said it targeted a militant command post, killing 19 fighters.

Israel has repeatedly ordered mass evacuations as its troops have returned to heavily destroyed areas where they had previously battled Palestinian militants. The vast majority of Gaza's population of 2.3 million people have been displaced by the 10-month old war, often multiple times.

Haifa's residents gaze warily on to the sprawling industrial port that flanks their Israeli city, knowing the potential for a major blast as they brace for possible bombardment from Hezbollah.

The historic city cascades down a steep hillside to the very edge of the port, a complex which contains Israel's biggest oil refinery, giant fuel tanks and other highly flammable targets.

Gaza's civil defense agency said Saturday an Israeli air strike on a school housing displaced Palestinians killed 93 people, as Israel's military accused militants of using the building as a command center.

AFP could not independently verify the toll which, if confirmed, would appear to be one of the largest from a single strike during 10 months of war between Israel and Hamas Palestinian militants.

Israeli troops launched a new assault Friday into the southern Gaza city of Khan Younis, targeting Hamas fighters who the military claims still operate there despite repeated offensives, as American, Qatari and Egyptian mediators renewed their push for Israel and Hamas to reach a cease-fire deal.

Israeli evacuation orders triggered yet another exodus of Palestinians from the heavily destroyed eastern districts of Khan Younis, where many had just returned less than two weeks ago — after the Israeli military's last incursion into the city in July.

An agreement to avoid a broad war in the region has likely been reached and the alternative might be a limited response against Israel by Iran and its allies or maybe no response at all, informed sources said.

The Lebanese file will also be separated from the rest of the axis while confrontations will increase on the border with Israel without breaking the rules of engagement, the sources told Kuwait’s al-Anbaa newspaper said.

Israel's Defense Minister Yoav Gallant, in talks with his U.S. counterpart Lloyd Austin, called for a swift agreement to secure the release of hostages held in Gaza, the Israeli military said on Friday.

"While working to secure Israel, minister Gallant raised the importance of swiftly achieving an agreement that will ensure the return of hostages held by Hamas in Gaza," the military said in a statement, adding the two agreed on "the urgency" of the issue.

Iran may be rethinking the scale and format of its planned reprisal against Israel after the assassination of Hamas’ political leader, Ismail Haniyeh, officials have suggested.

Fighting between pro-Iranian groups supporting the Syrian government and Kurdish-led forces left 11 civilians dead, a war monitor said Friday.

Six children were among those killed in intense shelling of the village of Dahla in the eastern region of Deir Ezzor, the Britain-based Syrian Observatory for Human Rights said.