Israel resealed border crossings with the Gaza Strip on Tuesday, Reuters reported. Israel had allowed 33 truckloads of supplies into Gaza for the first time in two weeks on Monday, and Israeli Prime Minister Ehud Olmert assured Palestinian President Mahmoud Abbas he would not permit a humanitarian crisis to develop there. "The crossings are shut because of ongoing rocket fire," Peter Lerner, a defence spokesman said, referring to several barrages of rockets fired from Gaza on Monday that slammed into Israeli towns, causing no injury. International aid groups said the supplies sent in on Monday were not enough to alleviate food shortages. Israel has also held up fuel shipments to Gaza's main power plant, leading to daily periodic electricity blackouts for many of 1.5 million Palestinians living in the territory. Israel had not allowed UNRWA, a United Nations agency that aids some 750,000 refugees in Gaza, to bring in supplies since Nov. 4 during cross-border fighting in which more than a dozen Palestinian fighters were killed.