The International Criminal Court's chief prosecutor has said she is weighing opening war crimes investigations into Palestinians as well as Israelis after Palestine joined the tribunal's jurisdiction last month.

Fatou Bensouda rejected Israeli fears of bias by the court, promising to consider the evidence "independently and impartially without fear or favor," in an interview published by Israel's liberal Haaretz newspaper on Friday.

The U.N.'s new Middle East peace envoy on Thursday urged Palestinian factions to unite and Israel to lift its blockade of the Gaza Strip, on his first visit to the territory.

"I strongly believe that it will hurt the cause of the Palestinian people if division, if the lack of unity, is not addressed as soon as possible," Nickolay Mladenov, who was appointed in February, told reporters in Gaza City.

Israel has returned 15 fishing boats it seized in recent years off the Gaza Strip, the army said, months after it fought a devastating conflict in the blockaded coastal territory.

Palestinian fishermen said it was the first time Israel had given vessels back, and demanded the return of dozens more.

Police in the Hamas-run Gaza Strip beat and arrested protesters on Wednesday at a youth rally in the north of the besieged Palestinian territory, an AFP correspondent said.

More than 400 demonstrators gathered in Shejaiya, a neighborhood in eastern Gaza City that was razed during a July-August war between Hamas and Israel, urging reconstruction and calling for an end to intra-Palestinian division.

A United Nations inquiry on Monday blamed the Israeli military for seven attacks on U.N. schools in Gaza that were used as shelters during the 2014 war.

"I deplore the fact that at least 44 Palestinians were killed as a result of Israeli actions and at least 227 injured at United Nations premises being used as emergency shelters," Secretary-General Ban Ki-moon said in a letter to the Security Council.

As relations between rival political factions hit rock bottom and with the prospect of a general election ever more distant, some Palestinians are left with a single voting outlet -- student elections.

The annual student council vote has all the flavour of a general election, pitting Fatah and Hamas, the two main political blocs, against each other.

Gaza militants fired at least one rocket at southern Israel on Thursday night as Israel wound up celebrations marking the anniversary of its creation, the Israeli army said.

Warning sirens sounded in "the southern communities of Sderot and Gevim following a rocket attack originating from the Gaza Strip. No damage reported," a military statement said.

A year after rival Palestinian nationalist movements Hamas and Fatah agreed to end their bitter divisions, the unity deal they signed appears to be on the brink of collapse.

This week, a ministerial delegation from the Ramallah-based consensus government headed to the Gaza Strip, the stronghold of Hamas, for what was to be a week-long visit focused on resolving a long-running dispute over employees.

A Palestinian court on Sunday dismissed a high-profile corruption case against exiled Gaza strongman Mohammed Dahlan, in a move that could open the door for his return to the occupied territories.

It was an unexpected end to a case which began in December with the former top Fatah official put on trial in connection with the alleged misuse of $17 million (15 million euros) in expenses.

Six months after donors pledged billions for devastated Gaza, only a quarter of the funds have materialized and not one destroyed home has been rebuilt, a coalition of aid groups said in a report Monday.

The report, "Charting a New Course: Overcoming the Stalemate in Gaza", warns that further conflict is likely unless the world takes a fresh approach to the battered Palestinian enclave, by releasing the promised funds, pushing for a permanent ceasefire and pressuring Israel to end its nine-year blockade.