Jerusalem  - Hamas authorities in Gaza should immediately launch a "credible investigation" into allegations of serious laws-of-war violations by its fighters during last winter's Israeli offensive in the Gaza Strip, Human Rights Watch (HRW) said Wednesday.

The call came in a letter HRW sent on Tuesday to Ismail Haniyeh, prime minister of the de facto Hamas government in the Gaza Strip.

A statement issued by HRW noted that a United Nations fact-finding mission into the Gaza fighting, led by Justice Richard Goldstone, called on Hamas and Israel to investigate within three months alleged war crimes by their respective forces during the December 27 to January 18 fighting.

The Goldstone report accused Israel of firing white phosphorous shells in populated areas during the fighting, and of using Palestinian civilians as "human shields" by forcing them to search the homes of militants.

It also said that the Palestinian rocket attacks against Israeli civilian centres, Israel's reason for launching the offensive, should be regarded as war crimes.

"Hamas, just like Israel, need to make clear to its forces that unlawful attacks on civilians will not be ignored," HRW official Sara Leah Whitson said.

Although Hamas has said it will probe the allegations against it, in previous occasions "it has failed to investigate any of its fighters and commanders who violated the rules of war," HRW said.

"In the past, Hamas tried to justify the unjustifiable by defending the unlawful rocket attacks. Having now promised to follow the Goldstone report's recommendations, Hamas has no excuse for not carrying out serious war crimes investigations," Whitson said.

In Israel meanwhile, calls are growing for the government to adhere to the Goldstone report's recommendations and probe the Gaza fighting.

The latest to lend his voice to the clamour was Deputy Prime Minister and Minister of Intelligence Dan Meridor, who told the Ha'aretz daily that the country should set up its won independent investigative committee.

"I have faith in the army and it is my duty to protect it, its commanders and its soldiers - and the most effective tool for this is serious self-examination," Meridor, a former minister of justice, said.

"A state that examines itself (protects itself from) harassment. Today, with the development of international law, one of the best means of defence is for a state to investigate itself," he said.

"A commission of inquiry should be established, also to examine the suitability of the rules of war to the new type of war that has been imposed on us," he argued.

Attorney-General Menahem Mazuz has also come out in favour of an official Israeli investigation.

Defence Minister Ehud Barak, on the other hand, opposes any internal probe, as does military chief of staff Gabi Ashkenazi.

The views Prime Minister Benjamin Netanyahu holds on the matter are not yet known.

On Tuesday the Israeli security cabinet met to discuss the implications of the report, hearing briefings from the foreign ministry, the head of military intelligence and the head of the national security council.

Discussions will continue, a government statement said.(dpa)