An international human rights group on Monday accused Israel of barring foreign researchers from entering the Gaza Strip to document abuses, saying the restrictions call into question Israel's stated commitment to investigating possible rights violations.

In a 47-page report, Human Rights Watch accused Israel of “systematically” preventing its researchers from visiting Gaza since 2008, only granting them one exceptional permit last year. The group also said that Egypt has prevented it and London-based Amnesty International from entering Gaza from its territory since 2012.

Israel and Egypt have imposed a blockade on Gaza, home to nearly 2 million people, since the militant Hamas group took over the territory in 2007. Israel and Hamas, a group sworn to Israel's destruction, have fought three wars since then.

International rights groups have accused both sides of committing war crimes, while the International Criminal Court is conducting a preliminary investigation into possible wrongdoing by both sides.

Israel has long accused Human Rights Watch of being unfairly biased against it. Last month, Israel refused to grant a work permit to the New York group's regional director, though it later allowed him to visit the country as a tourist.

Human Rights Watch said the Israeli restrictions cast doubt on the government's claims that it is conducting its own investigations and there is no need for the ICC to get involved.

“If Israel wants the ICC prosecutor to take seriously its argument that its criminal investigations are adequate, a good first step would be to allow human rights researchers to bring relevant information to light,” said Sari Bashi, Israel and Palestine advocacy director at Human Rights Watch.

The report also criticised Egypt for barring access to Gaza, and for Hamas' refusal to cooperate with investigators. It said Hamas has failed to protect local human rights workers from retribution and sometimes arrested or harassed its critics.

The absence of foreign rights investigators, who are less susceptible to Hamas pressure, limits the ability of Palestinian rights groups from documenting abuses by Hamas, the report said.

The three parties “should change their policies to protect the vital work of human rights groups seeking to protect Palestinians and Israelis from abuses by the authorities and armed groups,” Bashi said.

Cogat, the Israeli defence body that coordinates access to Gaza, denied barring rights groups from visiting the enclave.

It said in a statement that it allows over 1,000 people to cross through the border each day for a variety of purposes, including business, medical treatment and academic studies, and said all criteria are in line with security needs.

“We coordinate the crossing of many human rights organisations,” it said, naming the group “Doctors Without Borders” as an example. The statement made no mention of Human Rights Watch or Amnesty.

Cogat accused Hamas of trying to exploit Gaza civilians travelling through Israel for military purposes, "causing a constant tension between the will to help the civilian Gaza residents and our duty to protect the citizens of Israel".