Israel's assassination of Sheikh Ahmed Yassin has sparked calls for a greater international resolve to determine whether such actions are legal. Concern has been growing over an increased use of the tactic by the United States, as part of its global war on terrorism, and Israel, in attempting to counter the threat posed by Palestinian suicide bombers. The legal adviser to Israel's mission at the UN, Tal Becker, said yesterday that Israel had a range of options to deal with the threats it faced. 'There is no doubt that when it involves someone who is directly responsible for the perpetration of terrorist attacks in a situation where the scale and magnitude reaches the level of an armed conflict, it is legitimate,' he said. He rejected accusations that Yassin's death was an extrajudicial killing. He said the term was more aptly applied to the Palestinian leadership for its failure to prevent terrorist attacks. 'Yassin was responsible for hundreds of dead civilians in suicide bombings,' Mr Becker alleged. 'He's a legitimate military target not less in importance than Osama bin Laden.' Debate over the legitimacy of the strike centres on whether Israel's conflict with the Palestinians, or the US campaign against terrorism, can be classified as wars. If they are, the rules of war as governed by the Geneva Conventions can be applied - although these come into play only when sovereign states are involved. The Israeli-occupied Palestinian territories are not formally recognised in such a way. US law expert Ruth Wedgwood said that in a wartime setting, force was permitted against an enemy and those giving it orders, such as a military commander or an operative. If attempts to capture such people failed, or they refused to surrender, military action could be taken against them. That argument had been used by Israel in killing Yassin and could be applied to Palestinian president Yasser Arafat. 'He could not be killed as a political leader,' the Johns Hopkins University professor said. 'The argument they would have to make, and make persuasively, is that he was directing military operations.' But other experts believed Yassin's assassination violated international law. The University of Hong Kong's Lyal Sunga suggested Israel was carrying out law enforcement rather than fighting a war. 'There's a presumption of guilt and nobody gets to give their side of the story,' Dr Sunga said. 'It is an extrajudicial killing because there's no trial - it's that simple.'