The UN has announced its own inquiry into attacks that hit its facilities during the conflict
By Bethany Bell
BBC News, Jerusalem
There have been numerous calls for investigations into whether war crimes were committed during the recent Israeli offensive in Gaza.
The Geneva Conventions and additional protocols prohibit the destruction of property, "except when rendered absolutely necessary by military operations" and "indiscriminate attacks" affecting civilians.
Concerns about the number of civilian casualties and damage to buildings in Gaza have been raised - among others - by the United Nations, by the Palestinian Authority, the Arab League and by human rights groups.
But it is not clear whether the alleged violations count as war crimes or how people responsible might be held accountable.
During the three-week conflict, the United Nations says more than 40 people were killed when Israeli shells landed near a UN school and that warehouses at its main compound in Gaza City were hit by Israeli white phosphorus shells.
The UN says many people were sheltering in the school and the compound at the time of the attacks.
The UN Secretary General, Ban Ki-moon strongly condemned the attacks, although he did not use the term "war crimes". He has demanded "a thorough investigation into these incidents and the punishment of those who are responsible for these appalling acts."
Mr Ban has also announced a UN inquiry into the "casualties and damage" at United Nations property during the conflict.
Human rights groups, like Amnesty International and Human Rights Watch, say this is not enough.
They want a comprehensive international investigation into all the alleged violations of international law during the conflict - by Israel, by Hamas and by other Palestinian armed groups.
Human Rights Watch says it has been in Gaza investigating a number of allegations.
Both sides accused the other of putting civilians in harm's way
The claims against Hamas include firing unguided rockets at residential areas. The allegations against Israel include firing on ambulances or preventing them from reaching people in need. The claims against both Israel and Hamas include the indiscriminate use of weapons such as heavy artillery in densely populated areas, and using civilians as human shields.
Amnesty International says it has found "compelling evidence" that white phosphorus weapons were used by Israel in crowded parts of Gaza.
The substance, which can cause severe burns, is not illegal to use on the battlefield. But the international convention on the use of incendiary weapons says it shouldn't be used in civilian areas.
Mr Ban says such allegations should be investigated but not by the UN inquiry. He said these issues should be dealt with "by a proper judiciary, organisations, agencies at a national level".
Under international law, it is the responsibility of the state whose forces are accused to conduct their own inquiry, although the UN Security Council (and the General Assembly) has the power to establish special international tribunals, such as those set up for the former Yugoslavia and Rwanda.
Israel says it has the matter in hand.
The Deputy Spokesman at the Israeli Ministry of Foreign Affairs, Andy David, told the BBC that "Israel investigates all its actions regardless of outside calls." He said the country did not need "external intervention to conduct any investigation".
He said: "Israel acts according to international laws and with highest regards to morality during combat, even beyond the requirement of the law."
A spokesperson for the Israeli army said the hits near the UN school and on the UN compound were being investigated.
Some rights groups say images from the conflict prove the illegal use of phosphorus
The army says its "operations in the Gaza Strip were carried out in compliance with the rules of warfare under international law". It says it took "numerous measures to avoid causing harm to the civilian population".
In a written response to a BBC query, the army said it "always permitted the traffic of convoys and ambulances to deliver humanitarian aid and to perform emergency evacuations".
Regarding the use of white phosphorus, it said the army only used weapons "that are permitted by international laws and conventions. Even so, the matter is included in the inquiries conducted" by the military.
Human Rights Watch says Israel has a "poor record" of investigating allegations of serious violations by its forces and bringing prosecutions.
Israeli rights groups and some columnists have called for an independent commission to be set up in Israel, saying it is not sufficient for the Israeli military to investigate itself.
The Israeli army, and a number of human rights groups, say Hamas violated the rules of war by using civilians as human shields.
Human Right Watch says Hamas has done nothing to investigate.
A senior Hamas official, Ahmed Youssef, said allegations of violations were "completely baseless and nonsense", the result of the "Israeli propaganda machine of fabrication". He said there were "no violations by Hamas."
Mr Youssef added: "It was ridiculous to say human shields were used. No Palestinian would use another Palestinian as a human shield".
He said Human Rights Watch was not a credible institution, taking its findings from Israel. "They need to ask the people of Gaza what happened," he said.
Palestinian Authority President Mahmoud Abbas wants the International Criminal Court, the ICC, in the Hague to look into whether war crimes occurred in Gaza during the conflict.
But that is problematic.
The court's prosecutor can only instigate his own proceedings against a state that belongs to the court. Israel is not a formal member.
The UN Security Council can refer cases against non-members to the court, but such a move would likely be blocked by the United States, Israel's strongest ally.
A state party to the court can ask for a referral - but there is no Palestinian state.
At the end of January, in a bid to get the ICC involved in a Gaza investigation, the Palestinian Authority lodged a declaration recognising the authority of the court.
The ICC's prosecutor, Luis Moreno-Ocampo, is now examining whether the PA has the legal power to accept the court's jurisdiction.
He is also analysing whether the alleged violations fall within the category of crimes the Court has authority to deal with (genocide, crimes against humanity and war crimes); and whether national proceedings are taking place.
The legal issues are very complex and could take years to work out.
Other international lawyers say it is more likely that suspects could be prosecuted by a court in a third country under the principle of universal jurisdiction.
A Spanish judge is currently investigating the role of Israeli soldiers and security officials in a bombing in Gaza in 2002, in which a top Hamas militant, Salah Shehada and 14 other people were killed. There is concern in Israel that more cases like this could emerge.
In 2005, Israeli commander Brig Gen Doron Almog escaped arrest on war crimes charges after receiving a tip-off at Heathrow Airport. An Israeli official had warned him not to leave his plane, as a UK court had issued a warrant for his detention. European arrest warrants may discourage other Israeli commanders from travelling to Europe.
Israel's government has said it will provide legal protection for its soldiers against any foreign prosecution that may arise as a result of its military operation in Gaza.
The names of IDF commanders who took part in the Gaza offensive have not been published because of worries that foreign courts may pursue what the army calls "politically motivated legal action".