Nairobi, Kenya – A respected human rights organization has described Israel’s use of white phosphorus weapons in the recent Gaza conflict as “evidence of war crimes,” due to the indiscriminate impact on civilians.

The report, entitled “Rain of Fire: Israel’s Unlawful Use of White Phosphorus in Gaza” and published by Human Rights Watch, presents eye-witness testimony, ballistics evidence, photographs and other data, documenting how Israel illegally used phosphorus around residential neighborhoods, a school, market and hospital.

“In Gaza, the Israeli military didn’t just use white phosphorus in open areas as a screen for its troops,” said Fred Abrahams, co-author of the report. “It fired white phosphorus repeatedly over densely populated areas, even when its troops weren’t in the area and safer smoke shells were available. As a result, civilians needlessly suffered and died.”

During the conflict, the Israeli military claimed it was operating “according to international law” and denied they were using phosphorus shells. However, exposes by British newspapers The Times and The Guardian made these claims rather implausible. Israel later said it would conduct an internal investigation, but Human Rights Watch says this is not enough.

“Past Israeli Defense Force investigations into allegations of wrongdoing suggest that this inquiry will be neither thorough nor impartial,” Abrahams said. “That’s why an international investigation is required into serious laws of war violations by all parties.”

Phosphorus, which burns brightly and produces a cloud of thick smoke, has been used by the U.S., British and Israeli militaries as a way to mark targets or create smoke cover to conceal ground operations.

However, using phosphorus in battle is illegal under international law if used as an antipersonnel weapon or in civilian areas, as phosphorus particles burn deep into the flesh, causing horrific wounds. A 2001 article on phosphorus injuries from the medical journal Burns said “Death may result even with minimal burn areas.”

This would not be the first time the IDF has failed to display adequate due diligence in preventing civilian casualties. It used phosphorus and thousands of cluster munitions in the 2006 Lebanon war. In the aftermath, some 1 million unexploded bomblets lay scattered largely in civilian areas – 26 percent of the arable land in southern Lebanon was left contaminated by deadly ordnance.

As a signator of the 1949 Geneva Conventions, Israel has responsibility under international humanitarian law to protect noncombatants and use force with proportionality and restraint in densely populated civilian areas.

Gaza has an exceptionally high population density, making it extremely difficult to separate civilian and military targets. White phosphorus is a completely inappropriate weapon for this kind of environment. Using it in Gaza will make it very difficult for Israel to convince the global public that it occupies the moral high ground, despite radicalism, anti-Semitism and rocket attacks from Hamas.

The U.S. also cannot escape blame for this war crime. Human Rights Watch believes all the phosphorus munitions used in Gaza were made in the U.S. Moreover, as Israel’s most powerful ally, the U.S. has leverage over how the Israeli military conducts its operations.

The U.S. government and Congress should communicate their concern about the use of phosphorus to the Israeli military. They should make it clear that no country or military faction is ever above the laws of war and that phosphorus should never be used in civilian areas.