US Republican presidential candidate Mitt Romney has called on Libya's Transitional National Council (NTC) to “arrest and extradite” Lockerbie bomber Abdelbaset al-Megrahi. Romney urged Libyan opposition authorities to “extradite the mastermind behind the bombing of Pan Am 103 ... so justice can finally be done," AFP reported on Tuesday. Al-Megrahi, was convicted for December 1988 bombing of Pan Am flight 103 that killed 270 people when it exploded over the Scottish town of Lockerbie. He was then released from a Scottish jail, allegedly on compassionate grounds due to his terminal cancer on August 20, 2009, when he was said to have only three months to live. The Lockerbie mastermind, however, is still alive and made his first public appearance after nearly two years in July at a meeting supporting the Libyan dictator Muammar Gaddafi. Earlier on Saturday, New Jersey senators Robert Menendez and Frank Lautenberg also demanded al-Megrahi's extradition, urging NTC to send him back to the US. Libya's transitional authorities "should extradite al-Megrahi to the United States to answer for the bombing of Pan Am flight 103," Menendez told foreign policy magazine. "There would be no better signal to the world that a new Libya believes in justice and has every intention to adhere to international law,” he added. Most of those killed on the 1988 London to New York flight were Americans. Some senior US politicians believe al-Megrahi's release was a pre-planned plot orchestrated by Britain's energy giant British Petroleum and former UK officials.