Doctors in Gaza have reported previously unseen injuries from Israeli weapons that cause severe burning and deep internal wounds often resulting in amputations or death.

The injuries were first seen in July, when the Israeli military launched a series of operations in Gaza following the capture of an Israeli soldier by Palestinian militants.

Doctors said that, unlike traditional combat injuries from shells or bullets, there were no large shrapnel pieces found in the patients' bodies and there appeared to be a "dusting" on severely damaged internal organs.

"Bodies arrived severely fragmented, melted and disfigured," said Jumaa Saqa'a, a doctor at Shifa hospital, the main casualty hospital in Gaza City. "We found internal burning of organs, while externally there were minute pieces of shrapnel. When we opened many of the injured people we found dusting on the internal organs."

It is not clear whether the injuries come from a new weapon. The Israeli military declined to detail the weapons in its arsenal, but denied reports that the injuries came from a Dense Inert Metal Explosive (Dime), a new experimental weapon that causes a powerful blast but in a localised area. The Dime, while causing severe injuries to its target, is intended to limit what the defence industry calls "collateral damage."

In Gaza, Dr Saqa'a said the small pieces of shrapnel found in patients' bodies did not show up under x-ray. "We are used to seeing shrapnel penetrate the body making localised damage. Now we didn't see shrapnel, but we found the destruction," he said.

Most of the injuries were around the abdomen, nearly a metre up from the ground, he said. The doctors also found that an injured patient who had been stabilised after one or two days, might suddenly die. "The patient dies without any apparent scientific cause," he said. "So far we don't know why."

At the Kamal Odwan Hospital, in Beit Lahiya, deputy director Saied Jouda, said he had found similar injuries. "We don't know what it means - new weapons or something new added to a previous weapon," he said. "We had patients who died after stabilisation and that is very unusual."

He too found patients with severe internal injuries without signs of any large shrapnel pieces. Often there was severe burning. "There was burning, big raw areas of charred flesh," he said. "This must be related to the type of explosive material."

Photographs of some of the dead from Shifa hospital showed bodies that had been melted and blackened beyond recognition. Others showed internal bleeding without signs of shrapnel wounds. In several cases doctors amputated badly burnt limbs.

At least 250 Palestinians have died in Gaza since the latest military operations began and hundreds more have been injured. Neither of the doctors could give exact figures for the numbers of patients suffering the new injuries, although both said that most of those brought in during July showed signs of these injuries.

Dr Saqa'a of the Shifa hospital said the injuries occurred over a six-week period beginning in late June and running until early August, while Dr Jouda from Kamal Odwan hospital said he believed patients admitted even in recent days still showed signs of these unusual injuries.

The health ministry in Gaza has reported these injuries came from an "unprecedented type of projectile," and also noted severe burning and badly damaged internal organs, often around the abdomen. It called for an investigation into the cause of the wounds.

"You have complete burns that lead to amputation. You find shrapnel entering the body and leaving very, very small holes. We have never seen this before," said Khalid Radi, a spokesman at the health ministry.

Tissue samples from patients in Gaza were given to journalists from the Italian television channel RAI. In a documentary shown last week, the channel said the injuries appeared similar to the effects of the Dime. An Italian laboratory that analysed the samples reportedly said its results were "compatible with the hypothesis" that a Dime weapon was involved.

The weapon is new and in the US is still in the early stages of development. It has a carbon-fibre casing and contains fine tungsten particles rather than ordinary metal shrapnel. It causes a very powerful blast, but with a much more limited radius than other explosives.

However, the Israel Defence Force (IDF) denies the use of Dime weapons.

"The defence establishment is investing considerable effort to develop weaponry in order to minimise the risk of injury to innocent civilians. With regard to allegations of the use of Dime weaponry, the IDF denies the possession or use of such weapons," the military said in a statement.

"Due to operational reasons, the IDF cannot specify the types and use of weapons in its possession. In addition it should be emphasised that the IDF only uses weapons in accordance with the international law."

Some Israeli military experts have also dismissed the suggestion that a Dime weapon is involved. Isaac Ben-Israel, a professor at Tel Aviv University and a retired Israel air force general who was involved in weapons development, had seen some of the photographs of the dead and injured and said he believed the wounds came from ordinary explosives. "I can tell you surely that no one in Israel ever developed such a Dime weapon. It doesn't exist at all," he said.

The International Committee of the Red Cross (ICRC), which monitors weapons used in conflicts, said it had heard reports of similar injuries from Gaza and was collecting information on the case. "We haven't come to any sort of conclusion about what kind of weapon it was," said Bernard Barrett, an ICRC spokesman.