White phosphorus bombs used by Israeli forces in the Gaza Strip were produced and supplied by American arms manufacturers, according to an Amnesty International report that called for a comprehensive arms embargo on Israel.

The report documented dozens of weapons used by Israel and Hamas during the three-week offensive, concluding that both groups had carried out attacks on civilians constituting war crimes punishable by international law. The UN Security Council should impose an embargo until a mechanism was established to ensure that military equipment was not used to carry out such violations, said Amnesty.

Donatella Rovera, who headed the Amnesty fact-finding mission, said that the group had systematically collected and catalogued shells across Gaza, and traced serial numbers back to factory production lines in the US.

"All of the evidence points to the failure of America to exercise due oversight of what they sell to Israel, which is in breach of their own laws... which require that weapons will not be sold to a country where they will be misused. And the manner in which these weapons were used in Gaza is a war crime."

The human rights group said that weapons experts in Gaza found white phosphorus artillery shells marked M825 A1 – a US-made munition – throughout the coastal strip. The Times published photographic evidence that Israel was using the M825 A1 shells on January 8. At that time, Israeli military spokesmen denied that the weapon was being used, saying: "This is what we call a quiet shell – it has no explosives and no white phosphorus".

After the Gaza conflict, Israel acknowledged using white phosphorus in a manner "according to international law". Israeli media reported that the military was investigating the incident on January 15, when several white phosphorus artillery shells hit a UN headquarters in Gaza City, destroying tens of tons of humanitarian aid. Amnesty said that they had found shells with the marking PB-91K018-035, a lot number which indicates that they were assembled by Pine Bluff Arsenal (PB) in October 1991.

Mark Regev, spokesman for the outgoing Israeli Prime Minister Ehud Olmert, said that the report was "fundamentally flawed" and "tainted" by Hamas.

"Every effort is made to avoid having innocent civilians caught up in the crossfire between us and Hamas," Mr Regev said.

Hamas spokesman Fawzi Barhoum called the report "unfair", claiming that Hamas did not receive weapons from other countries, but defended themselves with "rifles and other primitive means".

Ms Rovera said that Hamas and other militant Palestinian groups had fired hundreds of rockets at civilians in Israel made of components from abroad.

"Though far less lethal than the weaponry used by Israel, such rocket firing also constitutes a war crime and caused several civilian deaths."

A number of other weapons were catalogued in the Amnesty report, including flechette shells – which release thousands of metal darts – and Dense Inert Metal Explosives (DIME). Amnesty also said that it found evidence of a new type of missile that dispersed into tiny cube-sized shrapnel pieces "designed to cause maximum injury". The report said that several children had been killed by the new weapon.

In another instance, Amnesty said that it found fragments of an AGM114 Hellfire missile, made by the Florida-based Hellfire Systems, a joint venture of Lockheed Martin and Boeing, that had been fired at an ambulance, killing three Palestinian paramedics and a boy in Gaza City on January 4.

The US has long been the largest arms supplier to Israel. Under a 10-year agreement negotiated by the Bush Administration the US will provide £21 billion in military aid to the country.

"As the major supplier of weapons to Israel, the USA has a particular obligation to stop any supply that contributes to gross violations of the laws of war and of human rights. The Obama Administration should immediately suspend US military aid to Israel", said Malcolm Smart, Amnesty’s Middle East director.

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