The UN Security Council voted unanimously Tuesday to extend the investigation into the assassination of former Lebanese prime minister Rafik Hariri until June 15, 2008. Belgian prosecutor Serge Brammertz told the council last week that the investigation into the killing of Hariri and 22 others in Beirut on Feb. 14, 2005 was making progress but will not be completed when the current mandate expires on June 15 of this year. He said in a recent report to the council that the probe is taking place in a "volatile political and security environment" which has hampered his ability to retain staff and to finish the investigation "in a timely fashion." The Lebanese government sent a letter to Secretary-General Ban Ki-moon asking for the Independent International Investigation Commission, which Brammertz heads, to be extended for one year when its mandate expires. Ban backed the Lebanese government's request in a letter to the council. The resolution adopted Tuesday, which was introduced by France, reaffirms the council's "strongest condemnation" of the terrorist bombing that killed Hariri, as well as other attacks in Lebanon since October 2004, and demanded that the perpetrators be brought to justice. The council expressed its willingness "to assist Lebanon in the search for the truth and in holding all those involved in this terrorist attack accountable." The resolution asks the commission to report to the council every four months, rather than every three months, "or at any other time as it deems appropriate." Brammertz, who said he did not know whether he would be staying on after June, stressed last week that the commission will never mention any names of people allegedly involved in the plot to assassinate Hariri publicly "because this will immediately have an impact on the right of defense." The first UN chief investigator, Germany's Detlev Mehlis, said the killing's complexity suggested the Syrian and Lebanese intelligence services played a role in Hariri's assassination. Four Lebanese generals, top pro-Syrian security chiefs, have been under arrest for 18 months, accused of involvement in Hariri's murder. The commission is also providing technical assistance to Lebanese authorities in 16 other cases including the November assassination of Lebanese Cabinet minister Pierre Gemayel and the near simultaneous bus bombings Feb. 13 on a busy commuter northeast of Beirut that killed three people and wounded 20.