In the first incident since the Gaza ceasefire went into effect Wednesday night, Palestinians reported a Palestinian youth was shot dead and nine were injured by Israeli gunfire when they tried to enter their fields near the southern Gaza border fence.   A source in the Israeli Southern Command source reported several hundred Palestinians had mobbed the Gaza border fence. When they attempted to breach it, a soldier first fired warning shots in the air, then at the lower limbs of the trespassers. The IDF is investigating the incident. The Palestinians have briefed Cairo, claiming the ceasefire grants them full access to all parts of the border region. Israel says that this issue is still up for discussion in negotiations still to come.