UN chief Ban Ki-moon on Tuesday paid what he called a “heartbreaking” first visit to the war-battered Gaza Strip where Israeli troops remained deployed on the third day of a ceasefire. Hours before the inauguration of US President Barack Obama, the army said a total troop pullout from Gaza was not under discussion although the ceasefire was holding firm. “For the moment, no one is talking about the total withdrawal of troops,” said army spokeswoman Avital Liebovich. Ban, describing the scenes in post-war Gaza as “heartbreaking,” called for those responsible for the bombing of UN buildings to be held accountable following Israel's 22-day war on Hamas militants. “It is an outrageous and totally unacceptable attack on the United Nations,” Ban said, speaking outside the still-smouldering main UN compound in Gaza City. “There must be a full investigation... there should be accountability through a proper judiciary system.” Ban became the first world leader to visit the enclave since Israel on Sunday halted the deadliest offensive it has ever launched on the Palestinian territory, which has been ruled by Hamas since June 2007. Four UN schools where Gazans were sheltering from the fighting were also hit by Israel. More than 40 people were killed in one such attack, according to medics and UN officials. Israel has said it made very effort to prevent civilian deaths and said troops were fired upon from inside or near each of the UN sites in question, a charge disputed by UN workers on the ground. Ban went on to accuse Israel of using “excessive force” in the conflict, but he also condemned Palestinian rocket fire on southern Israel as “completely unacceptable.” Also calling for an investigation were eight Israeli human rights groups who accused the army of ignoring the rules of war. They urged prosecutor general and government legal adviser Menachem Mazuz to act, describing the scale of casualties among women and children as “terrifying.” Palestinian health ministry figures list more than 1,300 people dead, including 410 children and about 100 women. Another 5,300 people were wounded - 1,855 of them children and 795 women. Meanwhile, Israeli soldiers shot dead a Palestinian farmer in the north of the strip on Tuesday, doctors said. An Israeli army spokesman said she could not confirm the report that the man had been killed near the town of Jabaliya by shots fired by troops close to Gaza's border with Israel. And two Palestinian children died in Gaza City when an Israeli shell they had been playing with exploded, doctors said. Israel launched its massive assault on Dec. 27 and started to pull out gradually from the territory on Sunday as Hamas and other militant groups pledged a week-long ceasefire. The Palestinian bureau of statistics reported 4,100 homes totally destroyed and 17,000 others damaged in the offensive. The rebuilding of Gaza looks set to become another battleground with Israeli Prime Minister Ehud Olmert warning Israel does not want Hamas to take control of reconstruction. “Israel believes that the reconstruction process must be led by international organisations in cooperation with the UN, Egypt and the Palestinian Authority,” he said. However, French Foreign Minister Bernard Kouchner said Paris will talk to Hamas if it shows it is ready to seek peace with Israel. “It is our opinion - and we realized this long ago - that Hamas was one of the interlocutors” in the Middle East peace process, he told French lawmakers on Tuesday. Former Irish president Mary Robinson and 2008 Nobel Peace Prize-winner Martti Ahtisaari are on a shortlist of candidates to lead a UN inquiry into violence in Gaza, a source at the world body said. Peter Hansen, a former Danish head of UNRWA, the UN agency providing aid for Palestinian refugees, is also on the list of potential heads of the mission alongside Robinson, who was UN High Commissioner for Human Rights until 2002, and seasoned international negotiator Ahtisaari, the source said. Uranium amo claim eyed The UN's nuclear watchdog said on Tuesday it would look into a claim by Vienna-based Arab ambassadors that Israel may have used ammunition containing depleted uranium in Gaza attacks. The IAEA said the request was made in a letter addressed to Director General Mohammed ElBaradei and was delivered by the Saudi Arabia ambassador on Monday on behalf of Arab diplomats. “We are circulating the letter to member states and will investigate the matter to the extent of our ability,” IAEA spokeswoman Melissa Fleming said. She said the IAEA had not yet decided on its course of action as it needs to check with member states first. The Israeli ambassador to the IAEA, Israel Michaeli, declined to comment on the letter. The IAEA has in the past contributed to studies on depleted uranium traces from ammunition in the Balkans which found it was highly unlikely that a reported increase in cancer risks there could be linked to the traces. Hamas declares victory Emboldened by surviving Israel's military onslaught, Hamas declared victory Tuesday in rallies attended by thousands supporters waving green Islamic flags atop the ruins in Gaza. The Islamic militants taunted Israel - one huge banner proclaimed Israel's defeat in Hebrew _ and said Gaza is just a stepping stone for eliminating the Jewish state.