A Palestinian from Fatah party has died Tuesday in a prison run by rival Hamas movement in the Gaza Strip, local sources said.

The detainee, Adel Rezeq, has been held at one of Hamas' internal security detention facilities since Thursday, sources from local rights groups added.

The sources noted that a call for an investigation would be issued soon, as the circumstances behind the death are still unknown.

The 50-year-old man was not suffering from any illness "and was in a very good condition when he was arrested," his brother, Muin, told Xinhua.

Hamas informed the family about the death and did not explain the reasons, the brother said, adding that the family refused to receive the body for burial unless an investigation is open and autopsy performed.

Since Hamas routed pro-Abbas forces and took over Gaza Strip in 2007, Rezeq had been detained several times and interrogated about his communication with the West Bank-based Palestinian National Authority, his brother said.

Hamas and Fatah have cracked down on their dissidents since the 2007 fighting, and several of political prisoners died in the Gaza Strip and the West Bank, human rights groups say.