A Palestinian rights group demanded on Sunday an investigation into the death of a man who appeared to have been tortured by security officials loyal to Hamas. In the West Bank, security officials said a Hamas loyalist committed suicide in a lockup in the northern town of Jenin on Sunday. Since Hamas seized power of Gaza in 2007, both groups have used detentions and beatings to intimidate opponents and cement their rule. Three people have died in Hamas lockups since the Islamist group seized power of Gaza and four have died in Palestinian Authority detention during the same period, according to human rights groups. The Gaza-based Palestinian Center for Human Rights said on Sunday that Hamas security officials took Jamil Shakoura, 51, into detention in late January, where he was blindfolded, handcuffed and taken to a detention center. There, the group said, he was beaten and forced to change his testimony. It was not immediately clear what kind of case security services were investigating. The group said that several days later, he died in a Gaza hospital from blows to his head. The man was not believed to be affiliated with a political group. A Hamas official said the matter is under investigation. However, Hamas officials have not made previous investigations public and it is not clear if anyone has been punished. In the West Bank on Sunday, security officials loyal to Fatah said in a statement that a detainee, Mohammed Hajj, 30, used his shirt as a noose to hang himself two days after he was arrested. The brief statement did not say why he was arrested, but said a forensics expert would examine the body. Hajj was a known Hamas loyalist and a father of three children. A relative, Nafiz Hajj, said they would demand an investigation.