An Israeli airstrike killed at least four Hamas militants as Israel steps up air raids on Gaza Strip in response to cross border rocket attacks. Tension in the streets of Gaza after six days of deadly factional fighting. Four Hamas militants were killed in an Israeli air strike early on Friday (May 18), taking the death toll among the Palestinian Islamists to seven in the hours since Israel vowed to hit back for Hamas rocket strikes. Israeli army said it had targeted a group of Palestinian militants who fired rockets into Israel. Local officials in Gaza said at least one missile from an F-16 jet hit a Hamas base near the Gaza Strip's eastern border with Israel. The attack happened at approximately 2 AM local time (2300gmt). Bodies of four members of Hamas were brought to a hospital morgue in Gaza City. An Israeli army official said the Hamas building which was attacked was suspected of housing a tunnel used to smuggle weapons and contraband into Israel. Israel said it launched the air strikes in response to cross-border rocket attacks. Friday's aerial attack came after 30 rockets were fired from Gaza into Israel within 24 hours, the Israeli army said. One rocket hit the Israeli town of Sderot, located about 5 km east of Gaza, minutes after Israeli Prime Minister Ehud Olmert had left the town. In response to the intense air assault, Hamas's armed wing threatened to resume suicide bombings in Israel. There was an uneasy quiet in Gaza early on Friday morning. Shops were closed and traffic was numb in the streets of Gaza after six days of fierce internal fighting verging on civil war. As the day warmed, a gunbattle also raged in the streets of Gaza City, centre of the densely packed coastal enclave of 1.5 million. Thirty-six hours after their leaders declared a ceasefire, gunmen from Hamas fought their secular rivals from President Mahmoud Abbas's long-dominant Fatah movement. Some 44 Palestinians, some of them unarmed civilians, were killed in continued faction fighting between Hamas and the secular Fatah group of President Mahmoud Abbas in the past week -- despite a ceasefire agreed late on Wednesday. ENDS.