Israel long thought its hi-tech security barrier blockading the Gaza Strip was impenetrable, brimming with razor wire, cameras and sensors and fortified with a concrete base against tunnels and remote-controlled machine guns.

But in the aftermath of the surprise Hamas onslaught, soldiers who were on guard duty have recounted the shocking moments when the militants launched their complex operation to breach Israel's "Iron Wall" around the enclave in multiple locations.

In mosques, football stadiums and towns across the Arab world, pro-Palestinian sentiment has surged after a shock Hamas attack on Israel, sparking a groundswell of solidarity for the Palestinians.

From Ramallah to Beirut, Amman, Damascus, Baghdad and Cairo, people have distributed sweets, danced and chanted prayers in support of "resistance" to Israel's long-standing occupation of Palestinian territories.

The White House said Tuesday it was taking Hamas threats to execute hostages seriously, as US President Joe Biden prepared to deliver remarks about Israel's war with the militant group.

Biden has not spoken in public since Sunday, and while the 80-year-old has staunchly backed Israel, his response to a possible hostage crisis and threat of a regional war is under the microscope.

Gaza's sole border crossing with Egypt, the only entry point not controlled by Israel, was hit by an Israeli air strike Tuesday for the third time in 24 hours, an AFP photographer and an NGO said.

The third strike against the Rafah crossing consisted of "four missiles" which targeted the Palestinian side of the crossing, local Egyptian group Sinai for Human Rights reported.

Witnesses had said the second strike hit the no-man's land between the Egyptian and Palestinian gates, damaging the hall on the Palestinian side.

The European Union and Gulf Cooperation Council called for sustained aid for the Palestinian territories on Tuesday following concerns it could be axed after the Hamas attack on Israel.

Foreign ministers from the two blocs met in the Omani capital Muscat following mixed messages over EU aid after Saturday's unprecedented assault which set off a war with Israel.

"They stressed the importance of sustained financial support for UNRWA (the UN Relief and Works Agency for Palestine refugees)," said a joint declaration read out by EU foreign policy chief Josep Borrell.

Israel said it recaptured Gaza border areas from Hamas militants on Tuesday, the fourth day of fierce fighting that has left thousands dead on both sides since the Islamists launched a surprise attack.

Prime Minister Benjamin Netanyahu has warned Israel's military campaign following Saturday's onslaught is only the start of a sustained war to destroy Hamas and "change the Middle East".

The families of Thai labourers held hostage by Hamas spoke Tuesday of their fears for their safety, after the Palestinian militant group threatened to kill civilian captives in its war with Israel.

At least 18 Thais have been killed and 11 seized since Hamas launched a surprise attack on Israel on Saturday.

Hamas dragged off around 150 people as hostages in its attack, and has said it will kill them one by one if Israel continues to hit Gaza with air strikes.

From fake accounts impersonating journalists to war-themed video games fueling false narratives, tech platforms are struggling to contain a tsunami of misinformation around Palestinian-Israeli hostilities after rolling back content moderation policies.

While major world events typically trigger a deluge of falsehoods, researchers say the scale and speed with which misinformation proliferated online following the weekend's deadly assault on Israel by the Palestinian militant group Hamas was unlike ever before.

Israel appears likely to stage a ground assault on Gaza in response to deadly weekend attacks by Hamas, risking close-quarters fighting in densely populated areas, including in underground tunnels and around hostages.

Israel's government on Monday said it would "immediately cut (its) water supply to Gaza" as part of a "complete siege" on the Hamas-controlled territory.

Syria has tortured tens of thousands of its people and maintains a "widespread and pervasive" system of "abhorrent treatment", world court judges heard on Tuesday at the first international case over the civil war.

Canada and the Netherlands have dragged Syria before the International Court of Justice, asking the court to demand urgent measures to stop the ongoing mistreatment of thousands still detained.

"Every day counts," Rene Lefeber, top representative for the Netherlands, told the court.