Israel has launched raids on and near several Gaza hospitals since the war erupted in October, claiming that fighters have used them as bases -- charges denied by the Palestinian militants.

Palestinians living near Gaza's largest hospital, Al-Shifa, have reported hellish conditions, including corpses in the streets, constant bombardment and the rounding up of men, who are stripped to their underwear and questioned.

Israel labelled the raids underway Monday around Gaza City's Al-Shifa hospital, and in the Khan Yunis neighbourhood surrounding Al-Amal hospital, "precise operational activities".

But the raids have sparked major fears for the patients and displaced people who are inside the facilities, which in some cases Israel has raided or cordoned off on more than one occasion.

The Palestinian Red Crescent said Al-Amal had all of its entrances surrounded by military vehicles and that hospital staff were prohibited from leaving.

The military said its operation in the Al-Amal neighbourhood included "raids on several terrorist infrastructure sites in the area and located explosive devices, RPGs (rocket-propelled grenades) and military equipment".

"Over 20 terrorists were eliminated in the Al-Amal area over the past day in close-quarters combat and aerial strikes," the army added.

The raid at Al-Shifa is now in its eighth day and the military reported detaining some "500 terrorists affiliated with the Hamas and Islamic Jihad terrorist organisations" and locating weapons in the area.

Israel has said that the operation will continue until the last militant is "in their hands", signalling an extended presence at Al-Shifa, which troops also raided in November.

The Red Crescent on Sunday said military vehicles had also surrounded Nasser hospital, about a one-kilometre (half mile) drive from the Al-Amal medical centre, but the situation at Nasser on Monday was unclear.