The United Nations called Tuesday for "a clear, transparent and credible investigation" of mass graves uncovered at two major hospitals in war-torn Gaza that were raided by Israeli troops, the AP reports. Credible investigators must have access to the sites, UN spokesman Stephane Dujarric told reporters, and added that more journalists need to be able to work safely in Gaza to report on the facts. The Palestinian civil defense in the Gaza Strip said Monday that it had uncovered 283 bodies from a temporary burial ground inside the main hospital in Khan Younis that was built when Israeli forces were besieging the facility last month. At the time, people were not able to bury the dead in a cemetery and dug graves in the hospital yard, the group said. The civil defense said some of the bodies were of people killed during the hospital siege. Others were killed when Israeli forces raided the hospital.