A growing number of international bodies are demanding an independent probe into mass graves recently discovered at multiple Gaza hospitals that were raided by Israeli troops revealing hundreds more Palestinian deaths as Israels military offensive in the besieged enclave surpasses 200 days.

As of Wednesday, Gaza health officials said that Palestinian medics have uncovered more than 300 bodies at the Nasser Medical Complex in Khan Younis, which Israeli troops occupied until their April 7 withdrawal. The U.N. Human Rights Council said Tuesday that medics found even more bodies in several mass graves on the grounds of Gaza Citys al-Shifa Hospital, which was once the territorys largest medical complex. Israeli forces conducted a two-week siege on the al-Shifa before withdrawing on April 1.

The harrowing discovery of these mass graves underscores the urgency of ensuring immediate access for human rights investigators, including forensic experts, to the occupied Gaza Strip to ensure that evidence is preserved and to carry out independent and transparent investigations with the aim of guaranteeing accountability for any violations of international law, senior Amnesty International official Erika Guevara Rosas said in a statement on Wednesday .