The UN High Commissioner for Human Rights Louise Arbour has warned that war crimes may have been committed in the conflict between Israel and Hezbollah. BBC News website World Affairs correspondent Paul Reynolds examines the issues.
Ms Arbour has stressed the need to protect civilians
What international law applies in this conflict?
The key principle of international law is to make a distinction between armed forces and civilians.
Although this conflict is not a war between states, and only Israel is a party to the Geneva Conventions, it is generally reckoned that the conventions and other humanitarian law should apply. And that in any case what is known as "Common Article 3" of the 1949 Conventions, which outlaw attacks on civilians, should be followed.
Strictly speaking this article covers an internal conflict where one party is not the government but again most lawyers say it should apply in this case. Its main provision aims at protecting civilians. "Persons taking no active part in the hostilities... shall in all cases be treated humanely," it says.
Is Israel committing war crimes by causing civilian casualties?
The 1949 Geneva Conventions aimed to end attacks purely or mainly against civilians, a tactic used heavily in World War II. Article 51 of the First Protocol to the 1949 agreements (updated in 1977) states: "The civilian population as such, as well as individual civilians, shall not be the object of attack."
Article 52 adds: "Attacks shall be limited strictly to military objectives..."
Therefore, there is a war crime if civilians are specifically attacked as civilians. However, it is different if they are killed as a result of a strike against a military or a "dual-use" target, (though see next answer for limits on such strikes).
Precautions to minimise casualties should be taken and the argument is about whether such precautions the Israelis say they have taken have been sufficient.
Indiscriminate attacks that target a wide area just to hit a few objectives or which hit military and civilian targets "without distinction" are outlawed by Article 51.
Questions could be asked here about Israeli artillery fire. And about air strikes under a situation described by Human Rights Watch: "The intentional launch of an attack in an area without regard to the civilian consequences or in the knowledge that the harm to civilians would be disproportionately high compared to any definite military benefit to be achieved would be a serious violation of international humanitarian law and a war crime."
Israel is not a party to the First Protocol though many experts and states say that this should apply in any case. And it remains a standard by which actions can be measured.
What about "dual-use" targets?
This is a more complex area in which the target might have dual use. For example, are airports, roads, bridges and power stations military targets or are they civilian? And what about houses and apartments claimed by the attacking side to be used by fighters yet with civilians in or near them?
Article 52 tried to resolve this: "Military objectives are limited to those objects which by their nature, location, purpose or use make an effective contribution to military action..."
Precautions should be taken. And if there is doubt, the decision should be that the target is civilian.
The question is whether the target is making an "effective" military contribution. If it is a justified attack, then the killing of civilians as a result is not a war crime. However, emphasis is put on the word "effective" so there has to be evidence for that not just a guess.
There might be a war crimes case if it can be shown that the attack in fact became principally or largely one in which civilians turned out to be the targets and that the attacker should have known that. This is obviously of relevance (and see what Louise Arbour says below).
The use of civilians as "human shields" to try to prevent attacks on military assets is also prohibited.
What about Hezbollah's attacks on Israel?
Hezbollah is sending rockets into Israeli populated areas without accurate guidance systems and is therefore reckoned to be attacking civilians. According to Human Rights Watch: "Deliberately attacking civilians is in all circumstances prohibited and a war crime."
And Hezbollah's capture of the two Israeli soldiers?
The "taking of hostages" is prohibited under Common Article 3. Both sides have used this tactic in the past.
What defines "proportionality"?
International law recognises that a state cannot take unlimited action in response to some incident. In the 19th Century, the British tipped an American boat, the "Caroline", over the Niagara Falls as they said it was helping Canadian rebels. It was subsequently agreed that retaliation was permissible but had its limits. In another case, in 1928, a tribunal held that German retaliation against some Portuguese troops for opening fire on them by mistake had been disproportionate.
In this case, the issue is whether Israel's actions following the capture of its soldiers were justified by their scale and tactics.
What is Israel's response?
An Israeli official said: "We feel that proportionality should be judged in terms of the threat we face. This is not just an issue of the kidnappings. Hezbollah has a huge arsenal and has fired 1,000 missiles at us. We are acting in self-defence.
"We are targeting only military objectives, including transport facilities that Hezbollah can use, but you have to remember that Hezbollah often hides in civilian areas. We sent flyers and gave other warnings to civilians to leave before our attacks."
And Hezbollah's reaction?
Hezbollah has argued that its initial raid was to capture the Israeli soldiers to be bargained for and that it has retaliated with rockets because of strikes against Lebanon and its civilians. The Hezbollah leader Sheikh Hassan Nasrallah said: "When the Zionists behave like there are no rules and no red lines and no limits to the confrontation, it is our right to behave in the same way."
What has the UN Human Rights Commissioner said?
The Commissioner, Louise Arbour, has raised the possibility of prosecution. "The scale of killings in the region, and their predictability, could engage the personal criminal responsibility of those involved, particularly those in a position of command and control," she said.
"International humanitarian law is clear on the supreme obligations to protect civilians during hostilities."
"Indiscriminate shelling of cities constitutes a foreseeable and unacceptable targeting of civilians", she said. "Similarly, the bombardment of sites with alleged military significance, but resulting invariably in the killing of innocent civilians, is unjustifiable."
Does this mean that there could be a war crimes trial?
That would not be easy. Israel is not a party to the International Criminal Court and nor is Hezbollah. There would have to be a separate procedure agreed by the UN.
Has the International Committee of the Red Cross spoken?
Yes. The Head of ICRC Operations, Pierre Kraehenbuehl said: "The civilian population is bearing an extremely heavy burden and consequences of the military action that is under way.
"The high number of civilian casualties and the extensive damage to essential public infrastructure does raise, in our view, serious questions regarding the respect of the principle of proportionality in the conduct of hostilities."