A Gaza man is being held on suspicion he bludgeoned his daughter with an iron chain, cracking her skull in a particularly brutal family "honor killing," two human rights groups said Wednesday, citing police and forensics reports. The groups' reports said that the assault was triggered by Jawdat Najjar's discovery that his daughter Fadia - a 27-year-old divorced mother of five - owned a cell phone. He suspected she used it to speak to a man outside the family, according to the groups' reports. Dr. Mohammed Sultan, who examined the victim, told The Associated Press that her head and face were bloodied, her body covered by bruises and that she suffered internal bleeding. On Wednesday, a northern Gaza police officer confirmed that Najjar turned himself in a day after the July 23 killing but did not give details. The officer spoke on condition of anonymity as he was not authorized to talk to the media. Three of the woman's brothers were also detained on suspicion that they acted as accomplices, said the rights groups Mezan and the Palestinian Center for Human Rights (PCHR), citing police and forensics reports. The groups did not say how they obtained the reports. Fadia Najjar was the 10th victim of a so-called "honor killing" this year in the Palestinian territories and among Arab communities in Israel, according to rights groups. In such killings, a woman's life is taken by male relatives who suspect her of inappropriate conduct. Such killings are still widespread in the Middle East, where a woman's perceived misconduct can hurt the standing of a family and where tradition says the "stain" can only be removed by shedding her blood. Traditionally, assailants have received light sentences, but the killing of Najjar shocked even activists used to detailing such crimes. Mezan and the PCHR said that Najjar's father used an iron chain to beat her, while also kicking and punching her for about 40 minutes until she died of a fatal blow to the head, said Mezan and the PCHR. "It's shocking," said Samir Zakout of Mezan. "But it's not surprising because killers know they won't be punished harshly." In the West Bank and Gaza, "honor killing" assailants serve between six months and three years in prison, said Mona Shawa of PCHR. In Jordan, officials said Wednesday they have set up special tribunals to deal with honor killings, hoping to speed up trials. The New York-based Human Rights Watch reported Wednesday that the Syrian government abolished a law that waived punishment for some honor killings and now allows judges to sentence perpetrators to at least two years jail.