Israel carried out deadly bombardments in Gaza for a second day on Saturday, hitting hundreds of targets, after a week-long truce with Hamas militants collapsed despite international calls for an extension.

Smoke again clouded the sky over northern Gaza, whose Hamas government said 240 people had been killed since the pause in hostilities expired early Friday.

According to the United Nations an estimated 1.7 million people in Gaza — around 80 percent of the population — have been displaced by eight weeks of war which have left them short of food, water and other essentials, with their homes destroyed.

The truce had allowed increased aid into Gaza via the Rafah crossing point with Egypt, but the Palestinian Red Crescent said Israel had told NGOs that "the entry of aid trucks has been suspended until further notice".

Both sides blamed each other for the breakdown of the truce, which had enabled the release of 80 Israeli hostages in exchange for 240 Palestinian prisoners.

During an unprecedented attack on 7 October, Hamas fighters broke through Gaza's militarized border into Israel, killed about 1,200 people, mostly civilians, and took around 240 Israelis and foreigners hostage, according to Israeli authorities.

Israel vowed to eliminate Hamas in response and unleashed an air and ground campaign that has killed more than 15,000 people, also mostly civilians, the Hamas authorities who run Gaza say.

Since the end of the pause, Israel's air, naval and ground forces have attacked more than 400 targets in Gaza, the army said on Saturday. The figure is roughly in line with the daily average number of strikes prior to the pause, according to figures released previously.

Warplanes hit "more than 50 targets in an extensive attack in the Khan Yunis area" of Gaza's south, the military added.

Separately, members of an Israeli armored brigade "eliminated terrorist squads and directed fire against terrorist targets in the north of the Gaza Strip", the military said.

Fighting spreads

Since the truce expired militants have fired rockets from Gaza towards Israel.

International leaders and humanitarian groups condemned the return to fighting.

"I deeply regret that military operations have started again in Gaza," UN Secretary-General Antonio Guterres said on X, formerly Twitter.

"Today, in a matter of hours, scores were reportedly killed and injured," UN humanitarian chief Martin Griffiths said. "Families were told to evacuate, again. Hopes were dashed."

Fighting also resumed on Israel's northern border.

The Lebanese militant group Hezbollah, which like Hamas is backed by Iran, said two of its members were killed Friday in Israeli strikes on Lebanon, as its fighters resumed attacks against Israeli targets following the end of the truce.

Israel's military said its artillery struck the sources of "launches" from Lebanon.

Syria said Israel carried out air strikes near Damascus on Saturday. A British-based war monitor said the strikes on "Hezbollah sites" killed two Syrian pro-Hezbollah fighters.

Hamas in October last year said it had restored relations with Syria's government. Israeli attacks on targets in Syria have intensified since the Israel-Hamas war began.

The United States said it was working with regional partners to reach another truce.

"We're going to continue to work with Israel and Egypt and Qatar on efforts to reimplement the pause," US Defense Secretary Lloyd Austin said on Friday.

Disappointment over hostages

The week of hostage-prisoner exchanges yielded tearful reunions of Israeli families with their released relatives and jubilation in the streets of the Israeli-occupied West Bank as Palestinians walked free from Israeli jails.

Twenty-five other hostages, mostly Thais, were also freed in separate arrangements.

The Israeli army said Friday that five more hostages had died, bringing the total number to seven, and 136 were still being held, including 17 women and children.

The end of the pause meant bitter disappointment for the families of those still not freed.

"We saw a chance for people to come out, be reunited with their families and resume their old lives," said Ilan Zharia, the uncle of 20-year-old Eden Yerushalmi, one of the women not to have been released.

Romania said it had been told by Israel that a Romanian-Israel hostage had died in Gaza.

In Dubai on Friday, Secretary of State Antony Blinken said the United States remained "intensely focused on getting everyone home, getting hostages back" and "pursuing the process that had worked for seven days" during the truce.

The Doctors Without Borders charity said one of the only hospitals still working in Gaza's north "was damaged in a blast" after the truce ended.

Guterres has warned of a "humanitarian catastrophe" in Gaza.

"The health care service is on its knees," Rob Holden, a World Health Organization senior emergency officer, told journalists from Gaza as explosions were heard in the background.

'Most dangerous place'

Outside Al-Ahli hospital in Gaza City, a man in a blue sweater bellowed in grief and turned his face and hands to the sky after viewing a dead boy in a body bag, AFPTV footage showed.

"What did he do wrong? God, what did we do to deserve this?" he yelled.

Thousands of children had already been killed in Gaza before the truce.

"Today, the Gaza Strip is once again the most dangerous place in the world to be a child," the UN children's fund executive director, Catherine Russell, said in a statement Saturday.

Visiting the region this week, Blinken, whose country provides Israel with billions of dollars in military aid annually, urged Israel to minimize innocent Palestinian casualties, "including by clearly and precisely designated areas… where they can be safe and out of the line of fire".

The Israeli military published a map of "evacuation zones" in Gaza that it said would enable residents to "evacuate from specific places for their safety if required".

Residents in various areas of Gaza were sent SMS messages on Friday warning that "a crushing military attack on your area" was coming, with the aim of eliminating Hamas.

Among those killed on Friday were three journalists, Gaza's Hamas rulers said.

Turkey's Anadolu state news agency confirmed the death of cameraman Muntassir al-Sawwaf and two others whom it did not name.