(Updates with Hamas interior ministry statement, paras 13-14)
GAZA, Jan 29 A Palestinian has accused Islamist Hamas militants in control of the Gaza Strip of torturing and killing his brother for publicly criticising them.
Osama Atallah, a teacher, was a supporter of the Fatah movement of Palestinian President Mahmoud Abbas. Hamas fighters drove Fatah militia out of Gaza in 2007 and fought Israel's army in a three-week war this month.
His brother, Bassam, said on Thursday that masked gunmen in two jeeps had arrived at the family home in the Gaza City on Tuesday. They identified themselves as members of Hamas internal security and arrested his brother Osama.
Bassam said the Hamas security service told the Atallah family that Osama would be released in a matter of hours. But a Hamas government official, who is also a member of the Atallah family, later denied the teacher was in custody.
The family subsequently received a telephone call from hospital that Osama Atallah was in critical condition.
He later died of his wounds.
About 1,300 Palestinians were killed in Israel's 22-day offensive of whom more than 700 were civilians, according to a Gaza human rights group. Ten Israeli soldiers were killed, including four in "friendly fire" incidents.
Ibrahim Abu An-Naja, a senior Fatah leader in the Gaza Strip, was quoted in a statement as saying four to eight members of Fatah were killed by Hamas during the war with Israel.
The statement said Abu An-Naja declined to give names. He said Hamas gunmen has fired on members of Fatah and shot them in the legs, and some had been placed under house arrest.
Fatah sources said Osama Atallah, a Fatah activist, had been threatened by Hamas "because of his public and continued criticism of the performance of the Hamas militias in Gaza".
They accused Hamas of "severely torturing and then strangling" Osama Atallah. They said bullets in his body could have been fired after he died.
Ehab al-Ghsain, the Hamas interior ministry spokesman said the Fatah accusations were being investigated and that once the results were known any guilty party would be held accountable.
The Israeli daily Haaretz reported on Thursday that Hamas "executed several dozen civilians" during and after Israel's assault on Gaza. Some were Fatah members but others were not politically affiliated, the paper said.
Haaretz quoted an Israeli intelligence source as saying a number of Palestinian agents working for Israel were intercepted by Hamas "because the intelligence they provided was used carelessly" by commanders intent on minimising troop casualties.
"It appears that in most cases Hamas suspected that their victims had collaborated with Israeli intelligence," it said.
Hamas in Gaza has not confirmed killing collaborators. But an Arab newspaper has carried a statement by an exiled Hamas official saying that the group had killed several.
The accuracy of some Israeli air strikes against individual militants in buildings, or against snipers shooting at Israeli forces, depended on the help of agents on the ground, according to some Palestinian security sources.
Haaretz said Israeli commanders with troops in Gaza were "very impressed that (intelligence services) could warn them with great precision of developments in their proximity". (Additional reporting by Ali Sawafta in Ramallah; writing by Nidal al-Mughrabi and Douglas Hamilton; editing by Angus MacSwan)