"Hamas has turned hospitals into command and control centres and hideouts for Hamas terrorists and commanders," Rear Admiral Daniel Hagari, Israel's chief military spokesman, told a news conference.

He showed photographs, diagrams and audio recordings he said showed how Hamas was using the hospital system and Al Shifa Hospital in particular to hide a variety of command posts and entry points into the extensive tunnel network under Gaza.

"Hamas terrorists operate inside and under Shifa hospital and other hospitals in Gaza," he said.

Hamas official Ezzat El-Reshiq, a member of the movement's political bureau, said on Telegram: "There is no basis in truth to what was reported by the enemy army spokesman," accusing Israel of spreading lies as "a prelude to committing a new massacre against our people".

The comments came as Israeli forces have massed outside Gaza and conducted raids into the enclave in preparation for an expected ground offensive in retaliation for the deadly Hamas attack on Israel that killed some 1,400 people.

Israeli jets and artillery have since pounded the enclave, destroying large areas and killing more than 7,000 people, according to Gaza health ministry figures.

It was not possible to verify Hagari's statements. The Israeli military has regularly accused Hamas of basing leadership and operational centres in residential areas or around schools or hospitals.

U.N. officials have called for a pause in fighting to allow aid into the enclave, where more than 1 million people have been displaced, and have warned they may have to cease operations if no fuel supplies get through.

Israeli officials have said that Hamas has significant reserves of fuels it uses for its own operations.

"There is fuel in hospitals in Gaza and Hamas is using it for its terrorist infrastructure," Hagari said.