Hamas militiamen have rounded up hundreds of Fatah activists on suspicion of "collaboration" with Israel during Operation Cast Lead, Fatah members in the Gaza Strip told The Jerusalem Post on Monday. They said the Hamas crackdown on Fatah intensified after the cease-fire went into effect early Sunday morning. The Fatah members and eyewitnesses said the detainees were being held in school buildings and hospitals that Hamas had turned into make-shift interrogation centers. Hamas has also renewed house arrest orders that were issued against thousands of Fatah officials and activists in the Gaza Strip shortly after the military operation started. A Fatah official in Ramallah told the Post that at least 100 of his men had been killed or wounded as a result of the massive Hamas crackdown. Some had been brutally tortured, he added. The official said that the perpetrators belonged to Hamas's armed wing, Izaddin Kassam, and to the movement's Internal Security Force. According to the official, at least three of the detainees had their eyes put out by their interrogators, who accused them of providing Israel with wartime information about the location of Hamas militiamen and officials. A number of Hamas leaders and spokesmen have claimed in the past few days that Fatah members in the Gaza Strip had been spying on their movement and passing the information to Israel. Two Hamas officials, Salah Bardaweel and Fawzi Barhoum, accused Palestinian Authority President Mahmoud Abbas and his "spies" in the Gaza Strip of tipping off the Israelis about the movements of slain Hamas interior minister Said Siam, who was killed in an IAF strike on his brother's home in Gaza City last week. The Fatah official in Ramallah said that, apart from being baseless, the allegations were aimed at paving the way for a ruthless Hamas attack on Fatah activists in the Gaza Strip. "They were afraid to confront the Israeli army and many Hamas militiamen even ran away during the fighting," he said. "Hamas is now venting its anger and frustration against our Fatah members there." Eyewitnesses said that Hamas militiamen had turned a number of hospitals and schools into temporary detention centers where dozens of Fatah members and supporters were being held on suspicion of helping Israel during the war. The eyewitnesses said that a children's hospital and a mental health center in Gaza City, as well as a number of school buildings in Khan Yunis and Rafah, were among the places that Hamas had turned into "torture centers." A Fatah activist in Gaza City claimed that as many as 80 members of his faction were either shot in the legs or had their hands broken for allegedly defying Hamas's house-arrest orders. "What's happening in the Gaza Strip is a new massacre that is being carried out by Hamas against Fatah," he said. "Where were these [Hamas] cowards when the Israeli army was here?" The activist said that Hamas's security forces had also confiscated cellular phones and computers belonging to thousands of local Fatah members and supporters. Relatives of Abed al-Gharabli, a former Fatah security officer who spent 12 years in Israeli prisons, said he was kidnapped by a group of Hamas militiamen who shot him in both legs after severely torturing him. Ziad Abu Hayeh, one of the commanders of Fatah's armed wing, the Aksa Martyrs Brigades, is reported to have lost his sight after Hamas gunmen put out his eyes. According to Fatah activists, Abu Hayeh was kidnapped from his home in Khan Yunis by Hamas militiamen. The Fatah men said that in a number of incidents, Hamas militiamen had kidnapped Fatah activists while they were attending the funerals of people killed during the war. In other cases, activists were detained and shot in the legs after they were spotted smiling in public - an act interpreted by Hamas as an expression of joy over Israel's military offensive. On Saturday night, three brothers from the Subuh family were abducted by Hamas militiamen and taken to the Abdel Aziz Rantisi Mosque in Khan Yunis, where they were shot in the legs, a local journalist told the Post. In a more recent incident, Hamas gunmen shot and killed 80-year-old Hisham Tawfik Najjar after storming his home and beating his four sons - all Fatah activists. Fahmi Za'areer, a Fatah spokesman in the West Bank, revealed that at least 16 Fatah activists had been executed by Hamas in the past few days. He strongly condemned the Hamas clampdown on Fatah and warned against a bloodbath in the Gaza Strip. A leaflet distributed by the Aksa Martyrs Brigades in various parts of the Gaza Strip called on Hamas to "respect the blood of the Palestinian martyrs" and stop pursuing Fatah members. The leaflet said that Hamas had placed hundreds of Fatah men under house arrest in the past 48 hours and was warning that anyone who failed to comply with these orders would be shot.