Palestinian Authority security officials said Sunday they could neither confirm nor deny reports that kidnapped BBC correspondent Alan Johnston had been executed by his captors in the Gaza Strip. A hitherto unknown group, calling itself the Tawheed and Jihad Brigades in Palestine, announced in a leaflet that was distributed in Gaza that its members had killed Johnston because of Israel's refusal to release Palestinian prisoners. The group, which PA security officials said was linked to al-Qaida, promised to release a video showing the execution of Johnston, 44, who was kidnapped in Gaza City more than a month ago. Until Sunday, no group had claimed responsibility for the abduction. The demands of the kidnappers also remained unknown, although a senior PA security official said they were demanding a ransom of $5 million. The announcement by the Tawheed and Jihad Brigades caught PA officials by surprise and drew strong condemnation from many Palestinians representing various political factions. If true, it would be the first time a foreign reporter was murdered by Palestinians. In the leaflet, the group held the PA presidency, the Hamas-led cabinet and the British government responsible for Johnston's killing. "The entire world knows of our just cause in demanding the release of our prisoners," it said. "Our demand was that all those who are responsible for the journalist release our prisoners who are being held in occupation jails." The group complained that while the international community responded with an outcry over the abduction of Johnston, "they did not take any action to secure the release of thousands of Palestinian prisoners." It said the execution of Johnston was intended to send a clear message that the Palestinian prisoners must be released. "We emphasize that our demand for the release of all the prisoners still stands," the leaflet said. "We will not relent until we release them all." PA Interior Minister Hani Kawassmeh said PA security forces did not have any evidence that Johnston had been killed. "We are still checking these reports and I hope they are untrue," he said. "We hope that the journalist will be reunited with his family soon." A senior PA security official told The Jerusalem Post there was mounting evidence that al-Qaida has been operating in Gaza for the past two years. "The border between the Gaza Strip and Egypt is open for many radical groups," he said. "Al-Qaida has at least four different groups in the Gaza Strip." A prominent Palestinian journalist in Gaza expressed fear that the reports about the killing of Johnston would deter many foreign journalists from entering the PA territories. "I hope the report about Johnston is not true," he said. "Otherwise, this would be a disaster for the entire Palestinian people." Defense officials said they were closely monitoring the reports that Johnston had been murdered. They said that for the past month, numerous attempts by the PA, the British government and Israel had failed to obtain information regarding his condition. Last week, the Post reported that Israel had, for the first time, allowed a Saudi Arabian security official to enter Gaza through the Rafah crossing on behalf of the British government in an attempt to locate Johnston. The defense officials said Johnston's abduction and monthlong disappearance should serve as a warning to foreign journalists who planned to report out of the Gaza Strip. If the report of Johnston's murder were true, the officials said, Israel would not take military action in Gaza. "There is not much that can be done if the reports are true," said one official who has been closely involved in the efforts to locate Johnston. "Israel will not go to war over this, and even Britain will have its hands tied." Earlier, another al-Qaida-linked group, calling itself the Righteous Swords of Islam, claimed responsibility for attacks on an Internet cafe and a Christian bookstore in Gaza City. Witnesses said the attack on the Protestant Holy Bible Society ignited a fire that burned many books. At least 45 Internet cafes and music shops have been blown up in different locations in Gaza over the past six months. Several Christian-owned institutions have been frequently attacked by extremist Muslims in the West Bank and Gaza Strip over the past few years. The attacks came less than 24 hours after the Hamas-led cabinet approved a new security plan aimed at ending the state of lawlessness and anarchy, especially in Gaza. Under the terms of the plan, Hamas militiamen will be incorporated into the PA security forces. PA Chairman Mahmoud Abbas on Sunday issued a presidential decree forming a National Security Council. PA Prime Minister Ismail Haniyeh will serve as Abbas's deputy in the new council, whose main task is to restore law and order. The appointment of Haniyeh was seen as a victory for Hamas, which for the first time will play a major role in security-related issues.