Israeli troops are advancing toward the al-Shifa Hospital in the Gaza Strip which they say houses a key stronghold of the Islamic group Hamas in the basement.

Israeli forces are continuing fierce attacks in northern Gaza. On Saturday, they announced that Israeli naval units had struck a Hamas weapons storage facility and infrastructure.

In an online post, Doctors Without Borders, the international NGO operating in the al-Shifa Hospital, said attacks against the hospital "have dramatically intensified".

Thousands of residents are said to be taking shelter at the hospital, the largest in Gaza.

Thirteen people died in an explosion that occurred there between Thursday night and Friday.

Doctors Without Borders said many patients remain in the hospital, including those who are in serious condition and cannot be moved.

A spokesperson for health authorities in Gaza said on Saturday that the hospital was forced to stop medical activity as it was running short of fuel.

Meanwhile, a spokesperson for the Israeli military warned residents in northern Gaza on Saturday to evacuate to the southern part of the enclave. It issued the warning on social media shortly after 10 a.m.

The Israeli military said it will halt military activity in the Jabalia refugee camp for four hours for humanitarian purposes.

Observers say the measure may reflect an agreement Israel reached with the United States on Thursday to hold four-hour daily pauses in the fighting.

The UN Office for the Coordination of Humanitarian Affairs estimates another 30,000 people evacuated to southern Gaza Strip on Friday through the route designated by the Israeli military.

Multiple explosions were reported along the route, raising concerns about further casualties.