The air force struck what it said were two arms depots in the center of the Gaza Strip, a rocket launching site and a terror activity site in the southern part of the Strip overnight Sunday.All targets were accurately hit, the IDF Spokesman’s Office said.Ben Hartman contributed to this report.The air strikes came as retaliation for six rockets that were fired from Gaza into the South late Sunday night. Four rockets were fired towards the Bnei Shimon council area and Netivot. The Iron Dome rocket defense system intercepted two rockets fired towards the Ashkelon Regional Council. No injuries or damage were reported in the attacks.As a result of the rocket fire, Defense Minister Moshe Ya'alon also ordered the closing of the Kerem Shalom and Erez border crossings between Israel and Gaza for the transport of commercial goods."Code Red" sirens were heard in the regional councils of Rahat, Netivot, Bnei Shimon and Lahavim.The rockets are thought to have been fired by Islamic Jihad but no organization has taken credit for the attack yet.The rockets have shattered a lengthy period of calm enjoyed by civilians in southern Israel.Early on Wednesday morning, "Code Red" warning sirens sounded in Ashkelon and surrounding areas.Shortly after the sirens went off, three rockets fell in Palestinian areas, Israel Radio reported. The rocket attack marked the first time Palestinian terrorists in Gaza have attempted to strike Israel for nearly two months. About 20 rockets have been fired by militant groups this year. Several rockets were fired during US President Barack Obama’s visit in March.The rocket fire broke a months-long period during which the Hamas regime in Gaza restrained elements in the coastal enclave, bringing about quiet. Since Operation Pillar of Defense in November, there have been few incidents of rocket fire.