Reformist Palestinian Prime Minister Mahmoud Abbas took office on Wednesday in a key step toward a U.S.-backed "road map" for Middle East peace, the official Palestinian news agency said. Palestinian authorities admitted only television crews, without their mobile phones, into the packed swearing-in ceremony at the battered headquarters of Palestinian President Yasser Arafat in the West Bank city of Ramallah. But a reporter from the official Palestinian news agency WAFA told Reuters that Abbas was the first minister to be sworn in on Wednesday. The landmark ceremony had already been marred by a new Palestinian resistance bombing in the Israeli city of Tel Aviv early on Wednesday, in which the bomber killed three people. The attack underlined the formidable challenge Abbas faces to curb militant violence in a 31-month-old Palestinian uprising. Abbas is the first-ever Palestinian prime minister, a post Arafat created under international pressure to cede some powers and implement democratic reforms. His cabinet includes both critics of Arafat and loyalists from within his Fatah movement. **PHOTO CAPTION*** Palestinian Prime Minister-designated Mahmud Abbas listens to Palestinina leader Yasser Arafat delivering a speech at the Palestinian Legislative Council (parliament) in the West Bank city of Ramallah.(AFP/Pedro Ugarte)