JERUSALEM ( CNN ) -- A rocket fired by Palestinian militants fell on a Gaza home and killed two children , Palestinian sources said Friday , the same day Israel opened three Gaza border crossings for the first time in 10 days . A truck carrying grain enters Gaza from Israel on Friday at the Karni crossing point , one of three Israel reopened . A third child was in critical condition . The children , all girls , were cousins -- the two who died were 7 and 12 , and the injured child is 5 , Hamas security and Palestinian medical sources said . The rocket struck a house north of Gaza City . In a separate development , the Israeli military said it allowed a Palestinian who was badly wounded by rocket fire Wednesday to enter Israel for treatment . The Palestinian entered Israel through the Erez Crossing between northern Gaza and Israel . Israel closed the crossing for all but humanitarian reasons because of rocket attacks from Gaza into Israel by Palestinian militants . But it opened three other crossings Friday , allowing fuel and commodities into the Palestinian territory for the first time in more than a week . About 80 trucks filled with commodities were expected to cross into Gaza . Among the goods were 400,000 liters of fuel and 120 tons of cooking gas . The decision to open the crossings at Kerem Shalom , Karni and Nahal Oz came after requests from international aid groups and Egypt , said Peter Lerner , a spokesman for the Coordinator of Government Activities in the Territories . In addition , he said , Israel has no desire to hurt the civilian population in Gaza . Lerner said whether to keep the crossings open would be a daily decision . United Nations assistance programs in Gaza have run out of flour and several essential pharmaceuticals , the U.N. Office for the Coordination of Humanitarian Affairs said . A tenuous six-month truce between the Hamas government in Gaza and Israel expired a week ago . Under the Egyptian-brokered deal , Hamas agreed to end militant attacks on Israel from Gaza , and Israel agreed to halt raids inside the territory and ease its blockade on humanitarian goods . In reality , the truce started breaking down two months ago . Rocket attacks by militants became more frequent , and Israel resumed airstrikes inside Gaza . Since then , dozens of rockets have been fired by Palestinian militants into Israel . Israel Defense Forces said about nine rockets have been launched from Gaza since midnight , pushing the three-day total to more than 110 . There are no reports of casualties in Israel . The crossings opened a day after Israeli Foreign Minister Tzipi Livni and Egyptian President Hosni Mubarak met in Cairo and Egypt expressed concern about the deteriorating humanitarian situation in Gaza . Livni criticized Hamas after her meeting with Mubarak . `` Hamas needs to understand that Israel 's basic desire to live in a tranquil region does n't mean that Israel is willing to accept ongoing shooting at its population , '' she said , according to the Israeli Foreign Ministry . `` Enough is enough . We can not accept this situation , and the situation will change . '' Israeli Prime Minister Ehud Olmert has threatened to respond to the escalating violence . He warned Hamas again Thursday in an interview on the Al Arabiya television network and seemed to suggest that time was running out . `` We do not want to fight the Palestinian people , but we will not allow Hamas to strike our children , '' Olmert said . `` I did not come here to declare war , '' he continued . `` But Hamas must be stopped -- and so it will be . `` I will not hesitate to use Israel 's strength to strike at Hamas and Islamic Jihad . How ? I do not wish to go into details here . ''
NEW : Militants ' rocket hits Gaza house , killing Palestinian cousins . NEW : Hamas says it will not negotiate with Israel until the release of all its prisoners and a halt to Israeli attacks on Gaza. Trucks filled with commodities cross into Gaza at three locations . Militants have fired 110 rockets since Wednesday , Israel says .