Israeli forces carried out arrests in Gaza's largest functioning hospital, health officials and the military said on Saturday, as airstrikes hit across the enclave and rain-battered Palestinians taking shelter in Rafah.

Israeli forces raided the Nasser Hospital in Khan Younis on Thursday as they pressed their war on Hamas, the Palestinian Islamist group that rules the enclave.

"Occupation forces detained a large number of medical staff members inside Nasser Medical Complex, which they (Israel) turned into a military base," said Gaza health ministry spokesman Ashraf al-Qidra.

The Israeli military said it was hunting for militants in Nasser and had so far arrested 100 suspects, killed gunmen near the hospital and found weapons inside it.

The Israeli incursion into the hospital has raised alarm about patients, medical workers and displaced Palestinians sheltering there.

About 10,000 people were seeking shelter at the hospital earlier this week, but many left either in anticipation of the Israeli raid or because of Israeli orders to evacuate, the Gaza health ministry said.

At least 83 people were killed in airstrikes across the Gaza Strip since Friday, health officials said, including one person on Saturday in Rafah, an area that borders Egypt and which Israel says is Hamas' last bastion.