Israel's ground forces in the Gaza Strip aimed to locate and disable Hamas militants' vast tunnel network beneath the enclave, the next phase in an Israeli offensive that has killed thousands of Palestinians.

Since Hamas gunmen killed 1,400 people and took some 240 hostages in an Oct. 7 cross-border raid, Israel has pounded Gaza from the air and used ground troops to divide the coastal enclave in two.

Gaza City, Hamas' main stronghold in the territory, is encircled. Israel says its troops have advanced to the heart of the densely-populated city while Hamas says its fighters have inflicted heavy losses on the invading forces.

Defence Minister Yoav Gallant said Israel had "one target - Hamas terrorists in Gaza, their infrastructure, their commanders, bunkers, communications rooms".

Chief Israeli military spokesperson Rear Admiral Daniel Hagari said that Israel's combat engineering corps were using explosive devices to destroy a tunnel network built by Hamas that stretches for hundreds of kilometres (miles) beneath Gaza.

Israeli tanks have faced heavy resistance from Hamas fighters using the tunnel network to launch ambushes, sources with Hamas and the separate Islamic Jihad militant group said.

It was not possible to verify the battlefield claims of either side.

ISRAEL SEEKS 'INDEFINITE PERIOD' OF CONTROL

Israelis have voiced fear that military operations could further endanger hostages, who are believed to be held in the tunnels. Israel says it won't agree to a ceasefire until the hostages are released. Hamas says it won't stop fighting while Gaza is under attack.

"I challenge (Israel) if it has been able, to this moment, to record any military achievement on the ground other than killing civilians," senior Hamas official Ghazi Hamad told Al Jazeera television.

"Gaza is unbreakable and will remain a thorn in the throat of the Americans and the Zionists," Hamad said.

Since Oct. 7, the Israeli bombardment has killed more than 10,000 Palestinians, around 40% of them children, according to counts by health officials in Hamas-ruled Gaza.

Washington has backed Israel's position that a ceasefire would help Hamas militarily. But U.S. President Joe Biden said on Tuesday he had urged Prime Minister Benjamin Netanyahu to undertake a pause in fighting.

Israel has so far been vague about its long-term plans if it achieves its stated goal of vanquishing Hamas. In some of the first direct comments on the subject, Netanyahu said Israel would seek to have security responsibility for Gaza "for an indefinite period" after the war.

But officials said Israel is not interested in governing the enclave. Gallant, the Israeli defence minister, said that after the war was finished, neither Israel nor Hamas would rule Gaza.