The fragile Gaza cease-fire was broken yet again on Tuesday afternoon when a mortar shell fired by terrorists landed in the Eshkol region, near Kibbutz Ein Hashlosha. No casualties or damage were reported in the attack and no Palestinian group immediately claimed responsibility for the fire. The attack came hours after Israel agreed to an Egyptian request and opened its border crossings with Gaza. Earlier Tuesday, two mortar shells landed near the Sufa border crossing, where humanitarian supplies are transferred into Gaza. One of the shells landed just inside Gaza and the other in Israel, the IDF said. Shortly after the mortar shell attack, a group of approximately 20 Gaza-belt residents staged a demonstration at the Nahal Oz crossing, blocking the transfer of fuel into the Strip. The residents were protesting the reopening of the terminal while projectile fire on the South continued. In all, 15 rockets and mortar shells have been fired from Gaza since the truce began. Defense Minister Ehud Barak agreed to reopen the crossings following a request by Egyptian intelligence chief Omar Suleiman, who said that keeping the crossings open might also help Israel achieve progress on the issue of captive IDF Cpl. Gilad Schalit. A Hamas delegation headed to Cairo Tuesday afternoon to discuss Schalit as well as the option of reopening the Rafah border crossing between Gaza and Egypt. Suleiman asked Barak in a phone conversation to open the other crossings and the defense minister agreed to allow the transfer of goods until the afternoon hours. In related news, an explosion went off early Tuesday at a Hamas training camp in Gaza, killing two members of the group and wounding three, both health and Hamas officials said. Hamas's armed wing said in a statement that the two were killed while carrying out a "holy mission," suggesting explosives were mishandled and went off prematurely. The IDF said it was not involved. AP contributed to this report.