As Israel’s three-week-old offensive against Hamas militants continues there have again been deaths from Israeli shell fire at a United Nations run school in the Gaza Strip. The UN says two young boys were killed and 14 people wounded when tank fire hit the school in the northern town of Beit Lahiya.A UN spokesman said there should be an investigation into possible war crimes as Israel had the coordinates of the school and knew it was being used as a shelter. Two weeks ago Israeli shelling killed 42 people who had taken refuge at a UN school. The UN Relief and Works Agency says about 45,000 Gazans are sheltering in its schools. White phosphorus, which causes severe burns, lying in the streets of Gaza was evidence of the continuing Israeli bombardment. The Israeli military said that overnight it attacked 50 targets including 16 tunnels, two mosques from which gunmen had fired on troops and eight rocket-launching pads. The Hamas run ambulance service says 1,200 people have now been killed and 5,300 wounded during the Israeli offensive.