Police arrested a Lebanese Islamic fundamentalist who was being investigated by a UN commission probing the assassination of former Prime Minister Rafik Hariri, security officials said. Mahmoud Abdel-Al, a member of the pro-Syrian Al-Ahbash Sunni Muslim Orthodox group, was detained in Beirut early Saturday upon orders from Lebanese Magistrate Elias Eid. His arrest was the first since chief UN investigator Detlev Mehlis released his findings into the investigation of Hariri's Feb. 14 slaying in a Beirut car bombing that killed at least 20 others. The officials, who spoke on condition of anonymity because they were not authorized to give official statements, said Eid based his decision to detain Abdel-Al upon a recommendation from chief UN investigators. Mehlis' report alleged that Abdel-Al called pro-Syrian Lebanese President Emile Lahoud on his mobile telephone minutes before the blast that killed Hariri. Lahoud denied receiving such a call. The UN inquiry claimed that shortly after, Abdel-Al also contacted one of four Lebanese pro-Syrian generals who have since been arrested in the probe. Police also seized unspecified documents during the raid on Abdel-Al's home, the officials said without elaborating. Abdel-Al's brother is a prominent figure in Al-Ahbash group, Ahmad Abdel-Al, whom Mehlis identified as a "key figure" in the ongoing investigation. Ahmad Abdel-Al had extensive contacts with top Lebanese security officials before and after the blast, and tried to hide information from investigators, according to the UN report. He was recently arrested in Beirut in connection with a weapons depot discovered in southern Lebanon in July. The Mehlis report implicated top Syrian and Lebanese intelligence officials in Hariri's murder. While the Lebanese government praised the report, Syria has rejected its findings as false, unprofessional and politicized. Lebanese legislator Saad Hariri, son and political heir of the slain former premier, praised the probe and called Saturday for an international tribunal to try the alleged killers. "Reaching justice presents the Arab and international community with additional responsibilities that prompt us to urge them to continue all aspects of the investigation in the crime and refer it to an international court that is capable of punishing the criminals," Hariri said in a televised speech.