ISLAMABAD - The UN inquiry commission constituted to probe the assassination of former Prime Minister Benazir Bhutto is arriving here today (Wednesday) on a four-day visit to initiate its investigation on Pakistani soil. The three-member commission is headed by Chiles Permanent Representative for the United Nations, Heraldo Munoz, while the other two members are Marzuki Darusman from Indonesia and Peter Fitzgerald from Ireland. The mandate of the commission is to collect data and information related to the assassination of Benazir Bhutto on December 27, 2007 in Rawalpindi, Pakistan. The commission will carry out only probe into Benazirs assassination and the punishment would de decided by the Pakistani government, said an official here on Tuesday desiring not to be named. The commission, he said, would submit its investigation report to the UN that would hand it over to Pakistan and the Pakistani government itself would make a decision about the punishment. He said that the UN commission had prepared the list of persons that it would meet for investigation but Pakistani government had full authority to permit or forbid the commission to access any Pakistani officer. The commission had asked for interviews with all the leaders of the Pakistan Peoples Party, who closely worked with Benazir Bhutto and also the police officials and other government functionaries who were with her in any capacity on the day of her assassination, the official said. Special Correspondent from United Nations adds: The three-member Commission of Inquiry into the facts and circumstances of the assassination of former Prime Minister Benazir Bhutto is on way to Pakistan for its first working visit to the country. The Commission, which is led by Chiles UN Ambassador Heraldo Munoz, is due to arrive in Islamabad within the next few days, UN Spokesperson Marie Okabe told the regular briefing on Tuesday. The commission began its activities on July 1 and already preliminary work has been underway on the ground, she said. Its mandate, agreed to in consultation with Pakistan, is to determine the facts and circumstances of the assassination, Ms Okabe said. The mandate does not include the conduct of a criminal investigation, she said. Responsibility for any criminal investigation and the prosecution of the perpetrators remains with the Pakistani authorities. The Commission will carry out its fact-finding activities in Pakistan and abroad, the spokesperson said. A final report on the commissions findings will be presented to Secretary-General Ban Ki-moon within six months - by the end of December 2009.The Secretary-General will share the report with the Government of Pakistan and submit it the Security Council, for information. The Pakistani govt had requested the United Nations to establish a commission to investigate the Ms Bhuttos killing. It has already paid 1.8 million dollars to the UN as seed money to cover its initial costs, and more countries are likely to contribute. Ms Bhutto was assassinated in gunshot and suicide bombing attacks on December 27, 2007 after addressing an election rally in a park in Rawalpindi.