(Adds officer abducted) By Nidal al-Mughrabi GAZA, Dec 14 (Reuters) - Palestinian intelligence agents arrested a member of a militant group in Gaza on Thursday in connection with the deaths of three young children earlier this week, witnesses and a security source said. The General Intelligence unit of the Palestinian security forces, a body allied to President Mahmoud Abbas, arrested Hisham Mukhaimar, a member of the Popular Resistance Committees, at his home in Gaza City, the group and witnesses said. A Palestinian security source, speaking on condition of anonymity, said the arrest was linked to the investigation into the killing on Monday of three schoolboys whose father was an intelligence official considered close to Abbas. The General Intelligence unit would not comment on the arrest. Because General Intelligence rarely arrest members of militant groups, Thursday's operation was considered significant, political sources said. A spokesman for the Popular Resistance Committees (PRC) demanded Mukhaimar's immediate release and threatened retaliation if he was not set free. "The PRC condemns the arrest by tens of masked men from the General Intelligence of a member of the PRC after they threw hand grenades and opened fire at his house," Abu Amir said. "We demand his immediate release or else." Hours later, masked gunmen abducted a General Intelligence member in Gaza City, security sources said. There was no immediate claim of responsibility. The security sources said they believed the abduction was related to Mukhaimar's arrest. Ambulance workers said two people were wounded during the arrest operation, including a member of the security forces. The killing of the three boys, all aged under 10, has stunned Gaza residents and deepened the divide between the main Palestinian political groups, Fatah and Hamas, raising the prospect of a sharp upsurge in internal violence. Fatah has accused Hamas of responsibility. Hamas denies involvement. On Wednesday, in apparent retaliation for the killing of the children, a Hamas judge who was also a member of the group's armed wing was shot dead on a street in the southern Gaza town of Khan Younis, further ratcheting up tensions.
