Explosions destroyed six cars belonging to members of the Hamas and Islamic Jihad militant groups in Gaza City on Sunday, witnesses said, injuring ** one but drawing threats of a response. The blasts hit a district dominated by supporters of Hamas and disrupted celebrations for the Muslim Eid el Fitr holiday. ** one claimed responsibility, but Hamas, which dominates the coastal enclave, has in recent months faced violent challenges from Palestinians sympathetic to Islamic State or al Qaeda, and who seek stringent religious rule in Gaza and open war with Israel.