"The International Federation of Red Cross and Red Crescent Societies is devastated to confirm the deaths of five members of our network due to the armed hostilities in Israel and the Gaza Strip," the IFRC said in a statement.

The organization pleaded for civilians and healthcare workers to be protected in the war that erupted on Saturday when militants Hamas launched an attack on Israel, which has pounded targets in the Gaza Strip in response.

"Today, Wednesday, in two different incidents, ambulances were hit killing four Palestine Red Crescent paramedics who were helping those in need," the Geneva-based IFRC said.

"Previously, on Saturday, an ambulance driver of Magen David Adom in Israel lost his life while driving an ambulance to treat injured people.

"The IFRC reiterates the call on all parties to respect their legal obligations under international humanitarian law. This is non-negotiable. Civilians, healthcare workers, health facilities, and civilian infrastructure must be respected and protected at all times. They are not a target."

The IFRC said it sent its deepest condolences to the families, friends, and colleagues of those killed on behalf of all 191 national Red Cross Red Crescent Societies.

The IFRC brings together more than 16 million volunteers around the world to help vulnerable people affected by disasters and health emergencies.

Israel on Wednesday kept up its bombardment of Hamas targets in the Gaza Strip, as Prime Minister Benjamin Netanyahu and a political rival announced an emergency government for the duration of the conflict that has already killed thousands.

Israeli soldiers sweeping battle-torn southern towns said they had found a total of 1,200 bodies.

Gaza officials reported more than 1,000 people killed in Israel's attack of air and artillery strikes on the crowded Palestinian enclave.