KABUL, Afghanistan, Dhu Al-Qa'dah 15, 1431, Oct 23, 2010, SPA -- A suicide attacker driving an explosives-packed car blew up the entrance to a United Nations office Saturday in western Afghanistan, allowing at least three other militants wearing bomb vests to rush into the building, officials said. An unknown number of U.N. employees were inside the building when it was attacked, said Dan McNorton, a spokesman for the United Nations Assistance Mission in Afghanistan. He had no information about any casualties. The suicide car bomber destroyed the gate and at least three other militants _ all wearing explosives vests _ went inside, said Nabiq Arleen, a spokesman for the provincial governor of Herat province. Afghan security forces exchanged gunfire with the attackers, killing at least one of them, said Ministry of Interior spokesman Zemeri Bashary. NATO troops joined Afghan forces in surrounding the site. Helicopters flew overhead, the Associated Press reported. --SPA 13:29 LOCAL TIME 10:29 GMT www.spa.gov.sa/829034