Suspected terrorists stormed a mosque close to Pakistan's army headquarters, killing at least 35 people during Friday prayers as they sprayed gunfire at worshipers and threw grenades before blowing themselves up, officials said. The strike was part of a wave of bloodshed that has killed more than 400 people in Pakistan since October. It was a bloody reminder of the resilience of militant networks despite army offensives against the Taliban in the northwestern regions bordering Afghanistan. At least four attackers took part in the assault an inside a heavily fortified area in the garrison city of Rawalpindi just a few miles from the capital. A local TV station reported that several high-ranking military officers were among the dead, but the army declined to confirm that. Witnesses said two of the militants entered the mosque, which was popular with army officers, while others ran into buildings nearby. With reporters prevented from getting close, security forces exchanged fire with the assailants for an hour before they blew themselves up or killing them. Nasir Ali Sheikh saw the attackers at the mosque as he walked there to pray. "They were killing people like animals," he said. "I couldn't understand what was happening." The attack was the third in Rawalpindi in the last two months. In the most high-profile incident, a team of militants attacked the army headquarters on Oct. 10 and held dozens hostage in a 22-hour standoff that left nine militants and 14 other people dead. Three helicopters hovered overhead while trucks carrying commando teams and ambulances raced through the cordoned-off area as soldiers kept onlookers and traffic away. The attack began when several gunmen staged an explosion to break through a checkpoint close to the mosque, said Yasir Nawaz, a police official at the scene. He said the installation included an army parade ground as well as the mosque, which was often used by military officers. Two of the assailants were able to enter the mosque and sprayed the congregation with gunfire and grenades, said military spokesman Maj. Gen. Athar Abbas. He said there were two other attackers. An intelligence official said 35 people were killed, their bodies taken to two hospitals close to the scene. Seventy others were wounded. The identities of the dead were not known. Violence in nuclear-armed Pakistan has escalated since the army launched an offensive in mid-October against Taliban militants in the northwestern tribal area of South Waziristan near the Afghan border. Soldiers have pushed deep into what was a militant stronghold, but many insurgents appear to have fled.