A government spokesman told the BBC: "We have a policy - we don't target civilians".The US and UN condemned the attack, which killed at least 16. Israel said its military responded to mortar rounds launched from near the school.More than 100 Palestinians were killed on Wednesday, Gaza officials said.The shelling of a market near Gaza City killed 17, while booby traps claimed the lives of three Israeli soldiers.At least 1,360 Palestinians have been killed since the current conflict began on 8 July. Most have been civilians.Some 58 Israelis have been killed, 56 soldiers and two civilians. A Thai worker in Israel has also died.'Hostile fire'The attack on the school in the Jabaliya refugee camp, which was sheltering more than 3,000 civilians, took place on Wednesday morning.UN Secretary-General Ban Ki-moon, who condemned the attack as "unjustifiable", said: "All available evidence points to Israeli artillery as the cause".Speaking to the BBC's Newsnight, Israeli government spokesman Mark Regev said: "We will investigate that. And if we find that it was errant fire from Israel I'm sure we will apologise."It's not clear to us that it was our fire but we know for a fact there was hostile fire on our people from the vicinity of the school."He accused Hamas, which controls Gaza, of hiding weapons in civilian facilities and UN shelters."We don't want to hurt innocent Gaza civilians. That's not our desire," he added.Chris Gunness, spokesman for the UN Relief and Works Agency (Unrwa) told the BBC that Israel had been told 17 times that the school was housing displaced people, saying the attack caused "universal shame".The attack on the school was also criticised by US State Department spokeswoman Marie Harf, although she did not name Israel."We do condemn the shelling of an UNWRA school in Gaza, which reportedly killed and injured innocent Palestinians including children and UN humanitarian workers," she said."Of course we would also condemn those responsible for hiding weapons in United Nations facilities in Gaza as well."Also on Wednesday, an attack on a market in Shejaiya killed 17 people, while an Israeli air strike killed seven people in Khan Younis, Palestinian officials said.Those attacks came during a four-hour humanitarian ceasefire called by the Israelis after the school incident.However, Israel said the truce was only partial and applied to areas where Israeli soldiers were not currently operating. It told residents not to return to areas they had previously been asked to evacuate.Hamas had rejected the truce as meaningless and "media exploitation".Israel said Palestinian militants continued to fire rockets from Gaza, with more than 50 launched on Wednesday.'Strong support'The current conflict, now in its 24th day, is the longest between Israel and militants from Gaza.A 2012 offensive lasted for eight days, and the 2008 conflict went on for 22 days.The Gaza Strip, sandwiched between Israel and Egypt, has been a recurring flashpoint in the Israel-Palestinian conflict for years.Hostilities increased after the abduction and killing of three Israeli teenagers in June, which Israel blamed on Hamas and which led to a crackdown on the group in the West Bank. Hamas denied being behind the killings.Tensions rose further after the suspected revenge killing of a Palestinian teenager in Jerusalem on 2 July. Six Jewish suspects were arrested over the youth's abduction and murder.Recent opinion polls in Israel suggest strong support for the military operation.Hamas says it will not stop fighting until a blockade, maintained by both Israel and Egypt, is lifted.Israel occupied Gaza in the 1967 Middle East war and only pulled its troops and settlers out in 2005. Israel considered this the end of the occupation, but it still exercises control over most of Gaza's borders, water and airspace. Egypt controls Gaza's southern border.(BBC)Bakudaily.az