Palestinians inspect a house destroyed in an Israeli strike in Khan Younis, Gaza Strip, on Monday. Reuters

Israel expanded its offensive against Hamas in besieged Gaza on Monday, as international concern deepened over the mounting civilian death toll in a war sparked by the October 7 attacks.

The return to open warfare after a truce between Israel and Hamas broke down has had ripple effects around a region on the cusp of a wider conflagration.

Meanwhile, Israel has been declaring some of the missing as dead in captivity, a measure designed to grant anxious relatives some closure.

A three-person medical committee has been poring over videos from the Oct. 7 rampage by Hamas-led Palestinian gunmen in southern Israel for signs of lethal injuries among those abducted, and cross-referencing with the testimony of hostages freed during a week-long Gaza truce that ended on Friday.

Since the expiry of the truce on Friday, fighting in Gaza has resumed between Hamas and advancing Israeli troops, as have Palestinian groups’ rocket launches toward Israel and Israel's air strikes on the Palestinian territory.

Over the weekend, Israeli air strikes on northern Gaza threw thick clouds of smoke and dust into the sky.

Israeli flares light the sky above Khan Yunis in the southern Gaza Strip. AFP

Of some 240 people kidnapped, 108 were freed by Hamas in return for the release by Israel of scores of Palestinian detainees as well as boosted humanitarian aid shipments to Gaza.

Since the truce, Israeli authorities have declared seven civilians and an army colonel as dead in captivity. Israel says 137 hostages remain in Gaza, their condition not always known.

On Sunday, the Israeli army reported a string of rocket salvos from Gaza into Israel, adding that most had been intercepted.

The Hamas-run government in Gaza and the official Palestinian news agency Wafa said a strike had hit the entrance of the Kamal Adwan hospital in the north of the territory late Sunday.

Several people were killed in the strike, the news agency said, while Hamas accused Israel on Telegram of a "grave violation" of humanitarian law.

Smoke rises at the site of a house destroyed in an Israeli strike in Khan Younis, Gaza Strip, on Monday. Reuters

Contacted by AFP, the Israeli military did not immediately comment on the alleged strike.

Israel says Hamas uses hospitals and other civilian infrastructure for military purposes — an accusation that the militant group denies.

"The IDF continues to expand its ground operation against main Hamas fronts in the Gaza Strip," Israel military spokesman Daniel Hagari said on Sunday.

"Wherever there is a Hamas stronghold, the IDF operates," he said, referring to the Israel Defense Forces.

Agencies