A woman reacts while people bury bodies of Palestinians killed in an Israeli strike, at the Nasser Hospital premises in Khan Younis on Monday. Reuters

Israeli forces, advancing deep into western Khan Younis in Gaza's bloodiest fighting so far in January, stormed one hospital and put another under siege on Monday, cutting the wounded off from trauma care, Palestinian officials said.

Troops advanced for the first time into the Al Mawasi district near the Mediterranean Coast, west of Khan Younis, the main city in southern Gaza.

There, they stormed the Al Khair Hospital and were arresting medical staff, Gaza health ministry spokesman Ashraf Al Qidra told Reuters. Qidra said at least 50 people were killed overnight in Khan Younis, while the sieges of medical facilities meant dozens of dead and wounded were beyond the reach of rescuers.

"The Israeli occupation is preventing ambulance vehicles from moving to recover bodies of martyrs and the wounded from western Khan Younis," he said.

The Palestinian Red Crescent said tanks had surrounded another Khan Younis hospital, Al Amal, headquarters of the rescue agency, which had lost contact with staff there.

"We are deeply worried about what is happening around our hospital," said Tommaso Della Longa, spokesperson for the International Federation of Red Cross and Red Crescent Societies.

"Ambulances cannot go in or out and we cannot provide any emergency health care to people in the area.”

The majority of Gaza's 2.3 million residents are now penned into Rafah just south of Khan Younis and Deir Al Balah just north of it, crammed into public buildings and camps of tents made from plastic sheets lashed to wooden frames.

Lines of cars and donkey carts piled high with belongings pushed south as Gazans sought to flee the bombardments.

"This is the seventh time I get displaced," said Gazan Mariam Abu-Haleeb, weeping in a car surrounded by her possessions. Ahmad Abu-Shaweesh, a boy, described having taken shelter in the Al-Aqsa University only to find the institution coming under attack.

"We hardly made it out of the university under the shelling. We didn't expect the tanks at the university's gates."

BURIED IN HOSPITAL GROUNDS

At Nasser Hospital, the only major hospital still accessible in Khan Younis and the largest still functioning in Gaza, video showed the trauma ward overwhelmed with wounded being treated on a floor splashed with blood.

Ahmed Abu Mustafa, an emergency doctor, said he hadn't slept for 30 hours and was treating 10-11 patients in an intensive care unit with four beds.

Outside, men dug graves within the hospital grounds because it was not safe to venture out to the cemetery. Authorities said 40 people were buried there.

In Brussels, Palestinian Authority Foreign Minister Riyad Al Maliki told reporters the situation in Gaza was out of control and asked the European Union to call for a ceasefire.

"The health system has collapsed. There is no way for injured Palestinians to be treated in the Gaza strip and they are not able to leave Gaza for treatment outside."