Gaza hospitals are overwhelmed with casualties from Israel's bombings and face critical shortages of drugs and medical supplies, the World Health Organization (WHO) said on Saturday.

The WHO, quoting Health Ministry officials in Gaza, said 382 people have been injured - 245 adults and 137 children.

"Many of those injured have been admitted to hospitals with severe burns, injuries from collapsing buildings and head injuries," the WHO said in a statement issued in Geneva.

Health authorities have declared an emergency situation in all hospitals to cope with patients, it said.

"Before the hostilities began, health facilities were severely over stretched mainly as a result of the siege of Gaza," the WHO said. Israel maintains a tight blockade on the Gaza Strip with the help of neighbouring Egypt.

The Gaza Ministry of Health's supplies of many life-saving drugs and disposable equipment were at "zero stock", it said.

"The Ministry of Health has postponed all elective surgeries due to the emergency and shortages in anaesthesia drugs,