Israel and Hamas have failed to conduct credible investigations of alleged war crimes during last year's Gaza war, Human Rights Watch said in a 62-page review of those efforts Sunday.

The New York-based group urged the international community to pressure both sides to launch independent investigations before a July deadline set by the United Nations. Earlier this year, the UN warned of further action if the deadline is ignored, though it is not clear if Israel and Hamas could end up before an international tribunal.

"A failure by governments to demand accountability for serious violations during the Gaza war will also reveal a double-standard in international concern for justice," the French news agency AFP quoted Human Rights Watch as saying.

"Governments that tolerate impunity in the Israeli-Palestinian conflict weaken their calls for accountability in places such as Sri Lanka, Sudan, and the Democratic Republic of Congo," HRW said in the report, entitled "Turning a blind eye."

"Ultimately, if domestic investigations in Israel and Gaza fail, then international prosecutions present the only chance for civilian victims of the armed conflict to obtain justice," it said.

Human Rights Watch researcher Fred Abrahams criticized the efforts on the part of both Israel and Hamas. "We want to encourage serious investigations in Israel and Gaza that look honestly at the many allegations of violations during the conflict," he said.

"To date, Israel's investigations have fallen way short of international standards, and Hamas has not conducted any serious investigations at all, said Abrahams."

The Israeli government has rejected demands to set up an independent inquiry outside the military.

Both Israel and Hamas have denied committing war crimes.

Israel launched its 22-day war on Gaza's Hamas rulers on Dec. 27, 2008, after years of rocket fire from Gaza on Israeli border communities. Israel unleashed massive force, killing some 1,400 Palestinians, including hundreds of civilians. Thirteen Israeli civilians and soldiers were also killed.

UN investigators headed by former war crimes prosecutor Richard Goldstone wrote in a report last year that they found evidence that both sides committed war crimes. Hamas was cited for indiscriminate rocket fire on Israeli civilians, while Israel was accused of using disproportionate force and intentionally harming civilians.