By Nidal al-Mughrabi and Maayan Lubell GAZA/JERUSALEM (Reuters) -Israeli air strikes pounded Gaza while the militant Islamic Jihad group fired hundreds of rockets into Israel on Saturday as a cross-border clash continued into a second day, killing at least six people, including four children. Hamas, the Islamist group which controls the enclave, said the children were among the dead from a blast close to the Jabalya refugee camp and blamed Israel. The Israeli military denied it was responsible, saying the explosion was caused by a failed Islamic Jihad rocket launch. It distributed a video whic…