Israel said its forces were operating in and around Gaza's biggest hospital, a chief objective in its campaign to destroy Palestinian Hamas militants that the army says stored weapons and ran a command centre in tunnels beneath the buildings.

Israeli troops forced their way into Al Shifa hospital in the early hours of Wednesday and spent the day deepening their search, the army said. An army video showed automatic weapons, grenades, ammunition and flak jackets it said were recovered from an undisclosed building within the complex.

"The troops continue to search the hospital in a precise, intelligence-based, manner," army spokesperson Rear Admiral Daniel Hagari said at a press briefing late on Wednesday. "We will continue to do so, in order to gather further information, to discover additional assets, and to expose the terror activities within the hospital."

U.S. President Joe Biden said that Hamas was committing war crimes by having its military headquarters under the hospital. He said Israel had gone into Al Shifa with a limited number of troops with guns.

"They were told...we discussed the need for them to be incredibly careful," Biden told reporters on Wednesday.

The Israeli military made no mention of finding any tunnel entrances in Al Shifa. It previously said Hamas had built a network of tunnels under the hospital. Hamas has denied it and dismissed the latest army statements.

"The occupation forces are still lying ... as they brought some weapons, clothes and tools and placed them in the hospital in a scandalous manner," Qatar-based Hamas senior member Ezzat El Rashq said. "We have repeatedly called for a committee from the United Nations, the World Health Organization and the Red Cross to verify the lies of the occupation."

Israeli forces raided the Shifa complex on Wednesday evening "for the second time in 24 hours" WAFA, the official Palestinian news agency, reported. Bulldozers and military vehicles were used, the agency said, citing local sources.

Hamas-affiliated Shehab news agency reported early on Thursday that Israeli tanks raided Al Shifa from the complex's southern side and that gunfire was heard in the area.

Israel began its campaign against the Islamist group that rules Gaza after militants rampaged through southern Israel on Oct. 7. Israel says 1,200 people were killed and some 240 people taken hostage in the deadliest day of its 75-year-old history.

Israel has vowed to destroy Hamas, but has not put forward a plan for after the war as to who would govern Gaza.

Biden said on Wednesday that he had made it clear to Israeli Prime Minister Benjamin Netanyahu that a two-state solution was the only way to resolve the Israel-Palestinian conflict and that occupying Gaza would be "a big mistake".

Biden told reporters he was doing everything in his power to free hostages held by Hamas militants, but that did not mean sending in the U.S. military.

Washington has boosted its military presence in the Middle East, sending two aircraft carriers and support ships to the region, to prevent the conflict spreading and to deter Iran, a long-time backer of Hamas, from getting involved.

Iran's supreme leader told the head of Hamas when they met in Tehran in early November, according to three senior officials: You gave us no warning of your Oct. 7 attack on Israel and we will not enter the war on your behalf.

Ayatollah Ali Khamenei told Ismail Haniyeh that Iran would continue to lend Hamas political and moral support, but wouldn't intervene directly, said the Iranian and Hamas officials with knowledge of the discussions who asked to remain anonymous to speak freely.

FIRST FUEL TRUCK ARRIVES IN GAZA

Israel has put Gaza's population of 2.3 million under siege and carried out an aerial bombardment. Gaza health officials, considered reliable by the United Nations, say about 11,500 Palestinians are confirmed killed, around 40% of them children, and more are buried under the rubble.

Israel has ordered the evacuation of the entire northern half of Gaza, and around two-thirds of residents are now homeless.

The first truck carrying fuel into Gaza since the start of the war crossed from Egypt on Wednesday to deliver diesel to the United Nations, though it will do little to alleviate shortages that have hampered relief operations.

The delivery was made possible by Israel approving 24,000 litres (6,340 gallons) of diesel fuel to be allowed into Gaza for U.N. aid distribution trucks, though not for use at hospitals, according to a humanitarian source.

The United Nations Security Council on Wednesday called for urgent and extended humanitarian pauses in fighting for a "sufficient number of days" to allow aid access. It also called in a resolution for the immediate and unconditional release of all hostages held by Hamas. The 15-member council overcame an impasse in four attempts to take action last month.

Israel has so far rejected calls for a ceasefire, which it says would benefit Hamas. A pause in fighting has been discussed, however, in negotiations mediated by Qatar to release some hostages taken in the Oct. 7 attack.

Qatari mediators were seeking a deal that would include a three-day truce, with Hamas releasing 50 of its captives and Israel to release some women and minors from among its security detainees, an official briefed on the negotiations said.