Nigerian police officers killed, 30 prisoners freed in attack on HQ ABUJA, Nigeria, Nov. 27 (UPI) -- Two officers were killed and dozens of prisoners were freed when a group of terrorists attacked the headquarters of a police unit in the Nigerian capital. One of the attackers was killed and six were arrested in the attack early Monday, the Nigerian newspaper Leadership reported. Officials said a group of armed men attacked the operational offices of the Special Anti-Robbery Squad in Abuja where Boko Haram militants were being held about 2 a.m. An anti-riot police officer and a police inspector were killed. The number of attackers was unclear. An unofficial report placed the number at 50. Police spokesman Frank Mba said in a statement there were "large numbers" of attackers. The spokesman said 30 prisoners escaped during the clash. Some 25 of the escapees were later arrested. Mba added that "no suspect held for terror-related charges escaped from SARS detention facilities. No explosive or IED-related materials were used in the attack.