By NAJIB JOBAIN and JACK JEFFFERY (Associated Press)

RAFAH, Gaza Strip (AP) — An Israeli strike flattened a home Thursday in an area of southern Gaza that the military had declared a safe zone as Israeli troops pressed their assault in the nearby city of Khan Younis. Palestinian hospital officials said the blast killed at least 12 people, almost all of them children.

Israel’s offensive has focused on Khan Younis, where the military said Thursday it has uncovered tunnels used by Hamas and battled fighters from the group that attacked into southern Israel on Oct. 7. Hamas has been designated as a terrorist organization by the United States, Canada and the European Union.

Israel has vowed to continue its campaign in Gaza until Hamas is destroyed. Now an apparent Israeli strike that killed a top Hamas leader in Beirut has stirred fresh fears that the conflict could expand into other parts of the region.

The killing of Sameh Arouri prompted warnings of retaliation from Hamas’ ally, the Lebanese Hezbollah militia. But there was no immediate escalation in the daily exchanges of rocket fire and shells between Hezbollah and the Israeli military over the two countries’ border.

After nearly three months, Israel’s bombardment and ground assault have killed more than 22,400 people in Gaza, more than two-thirds of them women and children, according to the Health Ministry in the Hamas-run territory. The ministry count does not differentiate between civilians and combatants.

The campaign has driven more than 85% of Gaza’s 2.3 million people from their homes. Israel’s assault leveled much of northern Gaza, and ground assaults in the south have pushed most of the population into smaller slivers of the territory. With strikes continuing to hit throughout Gaza, Palestinians say nowhere is safe.

On Thursday, a strike hit a house in Mawasi, a small rural strip on Gaza’s southern coastline where Israel’s military has said Palestinians should flee to escape the combat zone. The blast killed a man and his wife, seven of their children and three other children ranging in age from 5 to 14, according to a list of the dead who arrived at Nasser Hospital in Khan Younis.

There was no immediate response from Israel’s military.

Israeli troops pushed into Khan Younis in early December and have been battling Hamas there for weeks. The military said Thursday that its troops uncovered a large tunnel hundreds of meters (yards) long with an entrance in a field next to a mosque.

Footage released by the military showed it blasting into rubble buildings where fighters who reportedly fired on troops had hidden or that held Hamas infrastructure. Military officials did not elaborate.

Israel blames Hamas for the high civilian death toll, saying it operates within residential areas and has an extensive tunnel network beneath civilian sites.

Defense Minister Yoav Gallant said Israel is seeking a “clear victory” over Hamas, which has ruled the territory since 2007. The Oct. 7 attack from Gaza into southern Israel killed around 1,200 people, and some 240 others were taken hostage.

Israel appears far from achieving its goals of crushing Hamas and returning the estimated 129 hostages still held by the group. Gallant said several thousand Hamas fighters remain in northern Gaza, where Israeli troops have been battling fighters for over two months and where entire neighborhoods have been leveled.

U.N. associate spokesperson Florencia Soto Niño said officials from the U.N.’s humanitarian office and the World Health Organization on Thursday visited the Al Amal hospital in Khan Younis, which was reportedly hit by a deadly strike, and witnessed extensive damage.

The U.N. and its humanitarian partners have been unable to deliver aid to northern Gaza for three days, Soto Niño said.

The humanitarian office has warned that Gaza “is a public health disaster in the making,” she said.

Since Oct. 7, more than 400,000 cases of infectious diseases have been reported, Soto Niño said, including some 180,000 people with upper respiratory infections and over 136,000 cases of diarrhea — half in children under the age of 5.