Clancy Chassay investigates claims from three brothers that the Israeli military used them as human shields during the invasion of Gaza guardian.co.uk

The Guardian has compiled detailed evidence of alleged war crimes committed by Israel during the 23-day offensive in the Gaza Strip earlier this year, involving the use of Palestinian children as human shields and the targeting of medics and hospitals.

A month-long investigation also obtained evidence of civilians being hit by fire from unmanned drone aircraft said to be so accurate that their operators can tell the colour of the clothes worn by a target.

The testimonies form the basis of three Guardian films which add weight to calls this week for a full inquiry into the events surrounding Operation Cast Lead, which was aimed at Hamas but left about 1,400 Palestinians dead, including more than 300 children.

The Israeli Defence Forces (IDF) refused to respond directly to the allegations made against its troops, but issued statements denying the charges and insisted international law had been observed.

The latest disclosures follow soldiers' evidence published in the Israeli press about the killing of Palestinian civilians and complaints by soldiers involved in the military operation that the rules of engagement were too lax.

Amnesty International has said Hamas should be investigated for executing at least two dozen Palestinian men in an apparent bout of score-settling with rivals and alleged collaborators while Operation Cast Lead was under way.

Human rights groups say the vast majority of offences were committed by Israel, and that the Gaza offensive was a disproportionate response to Hamas rocket attacks. Since 2002, there have been 21 Israeli deaths by Hamas rockets fired from Gaza, and during Operation Cast Lead there were three Israeli civilian deaths, six Israeli soldiers killed by Palestinian fire and four killed by friendly fire.

"Only an investigation mandated by the UN security council can ensure Israel's co-operation, and it's the only body that can secure some kind of prosecution," said Amnesty's Donatella Rovera, who spent two weeks in Gaza investigating war crime allegations. "Without a proper investigation there is no deterrent. The message remains the same: 'It's OK to do these things, there won't be any real consequences'."

Some of the most dramatic testimony gathered by the Guardian came from three teenage brothers in the al-Attar family. They describe how they were taken from home at gunpoint, made to kneel in front of Israeli tanks to deter Hamas fighters from firing, and sent by Israeli soldiers into Palestinian houses to clear them. "They would make us go first so if any fighters shot at them the bullets would hit us, not them," 14-year-old Al'a al-Attar said.

Medics and ambulance drivers said they were targeted when they tried to tend to the wounded; sixteen were killed. According to the World Health Organisation, more than half of Gaza's 27 hospitals and 44 clinics were damaged by Israeli bombs.

In a report released today, a medical human rights group said there was "certainty" that Israel violated international humanitarian law during the war, with attacks on medics, damage to medical buildings, indiscriminate attacks on civilians and delays in medical treatment for the injured.

"We have noticed a stark decline in IDF morals concerning the Palestinian population of Gaza, which in reality amounts to a contempt for Palestinian lives," said Dani Filc, chairman of Physicians for Human Rights Israel. The Guardian gathered testimony on missile attacks by Israeli drones against clearly distinguishable civilian targets. In one case a family of six was killed when a missile hit the courtyard of their house. Israel has not admitted using drones but experts say their optical equipment is good enough to identify individual items of clothing worn by targets. The Geneva convention makes it clear medical staff and hospitals are not legitimate targets and forbids involuntary human shields.

The army responded to the claims. "The IDF operated in accordance with rules of war and did the utmost to minimise harm to civilians uninvolved in combat. The IDF's use of weapons conforms to international law," it said. The IDF said an investigation was under way into allegations hospitals were targeted. It said Israeli soldiers were under orders to avoid harming medics, but: "However, in light of the difficult reality of warfare in the Gaza Strip carried out in urban and densely populated areas, medics who operate in the area take the risk upon themselves."

Use of human shields was outlawed by Israel's supreme court in 2005 after a string of incidents. The IDF said only Hamas used human shields by launching attacks from civilian areas. An Israeli embassy spokesman said any claims were suspect because of Hamas pressure on witnesses. "Anyone who understands the realities of Gaza will know these people are not free to speak the truth. Those that wish to speak out cannot for fear of beatings, torture or execution at the hands of Hamas," the spokesman said in a written statement.

However, the accounts gathered by the Guardian are supported by the findings of human rights organisations and soldiers' testimony published in the Israeli press.

An IDF squad leader is quoted in the daily newspaper Ha'aretz as saying his soldiers interpreted the rules to mean "we should kill everyone there [in the centre of Gaza]. Everyone there is a terrorist."

• This article was updated on Tuesday March 24 2009 to reflect changes made for the first edition of the Guardian newspaper.