ISLAMABAD (Agencies) - Police searched for clues Thursday as to who carried out a failed assassination attempt on Prime Minister Yousuf Raza Gilani, a day after sniper fire struck his motorcade. The premier was not in the targeted vehicle at the time, but the brazen daytime attack on Wednesday underscored security fears in the world's only nuclear-armed Islamic nation ahead of Saturday's presidential election. Interior advisor Rehman Malik said investigations were underway but declined to give any details. "We hope the investigations will be finalised in two or three days," he said. Security officials told AFP that police were examining the site on the main highway to the airport and that the government was awaiting a ballistics report. Sniffer dogs were taken round the area but officials said no clues were found. A police investigator said the apparent assassination bid was likely "symbolic." "What is clear is that they could never have breached the bulletproof windows with this kind of fire," he said. A government official said a preliminary police report was inconclusive on what exactly hit the prime minister's vehicle. A police official meanwhile said that if the vehicle had been hit by a long-distance sniper shot, the marksman would have been of very high quality. "A single sniper will find it very hard to hit a moving car twice within a short space," the official said. Meanwhile, Koral Police Station Islamabad has registered the First Information Report (FIR) under Anti-Terrorism Act, 7 and 324 PPC (Attempt to murder) for attacking the Prime Minister's convoy on Islamabad Highway. The complainant has been lodged on behalf of Abdul Razaq who is the gunman of Prime Minister, the police sources said. The attack on PM's convoy was made by some unidentified attackers on the instructions of some terrorist outfits, the police sources said quoting the statement of complainant in the report. meanwhile: the initial investigation report on firing at Prime Minister's car has been presented to the Advisor to the Prime Minister on Interior Rehman Malik whereas IG Punjab has been directed to submit a detail report as regard to the incident. The initial report has been prepared under the supervision of Director National Police Bureau Tariq Khosa. According to sources, Special Investigation Group (SIG) of FIA has confirmed that the car included in PM's motorcade was damaged by bullets in contrast to an initial perception that stones damaged it.