The United Nations said Friday the humanitarian situation in Gaza Strip has become "very serious and dire" and urged Israel to open border crossings to allow Palestinians to receive relief aid, according to dpa. John Holmes, the chief UN humanitarian emergency coordinator, said the crossing points between Israel and the Palestinian territories should remain open for longer. Holmes made the appeal as fighting increased and Israel launched more airstrikes into Gaza. "I hope the people are listening to what we are saying, the situation is very serious and dire," he said. The UN has been urging both sides to exercise restraint and in particular Israel not to use force disproportionately. Israel, in response to rocket fire from Palestinian militants into its southern towns, has closed major crossing points into Gaza, severely curtailing traffic of goods into the territory dominated by the Hamas militant group and preventing Palestinians from seeking jobs in Israel.