Palestinian militants in Gaza over the weekend fired about 40 rockets at cities and towns in southern Israel, for the first time since Israeli soldier Gilad Shalit was released from Hamas captivity two weeks ago. The attacks started on Wednesday and increased after an Israeli airstrike on Saturday killed a senior militant in charge of rocket makeshifts from the Islamic Jihad movement, which was discontented at the efforts made by its sometime ally, Hamas, to impose a cease- fire with Israel. Militants fired salvos at southern cities and towns of Israel, killing a resident of coastal Ashkelon and wounding several others. Israeli responsive strikes have killed nine militants, mostly from Islamic Jihad. \"It seems to be an initiative of the Islamic Jihad, not coordinated or allowed by Hamas. And probably Hamas is now trying to restrict the actions,\" Dr. Ephraim Kam of Tel Aviv University told Xinhua Sunday. Kam said that Gaza-ruling Hamas has probably been pressuring other groups in the coastal enclave to refrain from any attacks on Israel while the details of the prisoner swap deal for Shalit were being worked out. Israel released 477 Arab and Palestinian security prisoners, the first batch in a prisoner swap deal reached by Israel and the Islamic Hamas movement, two weeks ago in exchange for Shalit. Most of the prisoners were Hamas members, and massive street celebrations were held in Gaza upon their arrival. \"Hamas wants to enjoy the benefits, and to make political gain following the prisoner deal. Any fighting in and around Gaza isn\'t in the interests of Hamas at this moment,\" Kam said. He further argued that, now that the deal has been completed, Islamic Jihad probably regarded themselves as being less committed to any cease-fire and they tried again, as they have done in the past, to test the limits of Israel\'s response. \"There is no interest from Israel\'s point of view to continue this deterioration or to carry out another Operation Cast Lead,\" Kam said, referring to the large-scale ground operation in Gaza that Israel launched in December 2008. Israel argued that the offensive was meant to quell the increasing number of rockets and mortars fired by Palestinian militant groups. However, \"if this deterioration continues, Israel will have no choice but to take more steps against Hamas and Islamic Jihad,\" Kam added. Moshe Marzuk, a researcher at the Interdisciplinary Center in Herzliya, believes that in addition to the standoff between Hamas and Islamic Jihad, the rocket attacks were meant to prove that even after the Shalit deal, there are still groups willing to continue attacks against Israel.\" \"It\'s wrong to make a difference between Hamas and Islamic Jihad,\" Marzuk said, because this allows Hamas to argue that they are not able to control other groups in Gaza. However, Hamas has proved that it is the most powerful group in Gaza, Marzuk said, adding that Israel will hold Hamas responsible for any hostilities emanating from Gaza, no matter who actually launches the rocket. He argued that Israel must show Hamas that the price they would pay for allowing such continued attacks is very high. Israel has a number of ways to make its point, \"including large scale military operations targeting Hamas government infrastructure,\" Marzuk said. \"The response can\'t only target the militants in Islamic Jihad, Hamas is the government responsible for what\'s happening in all the territory of the Gaza Strip,\" he added.