Unidentified gunmen riding on motorcycles ambushed an army vehicle in the Pakistani capital on Thursday, unleashing a hail of bullets that killed a Brigadier and his guard and injured another soldier in the latest in a wave of deadly attacks targeting the security forces. Gunmen on a motorcycle killed Brigadier Moin Haider and his driver, city police official Tahir Alam said. A guard was wounded. "Witnesses have told us two men came on a motorcycle and opened fire," said another city police official Abdul Qadir. Military spokesmen were not available for comment. Witnesses said three armed gunmen on two motorcycles opened fire at the army jeep in a commercial area with several automobile workshops. The Brigadier and his guard were killed instantly in the firing that took place around 9 a.m local time, state-run PTV reported. Television footage showed the vehicle was riddled with bullets and its windscreen shattered. The windshield was hit by more than 10 bullets. Another soldier who was driving the vehicle was injured. The gunmen fled from the scene unchallenged. Security forces cordoned off the area and sealed several roads after the attack which was the second assault in Islamabad in three days. A search was launched to nab the attackers. "Two (soldiers) are dead, including one officer. There is one wounded, he is an army soldier," Doctor Altaf Hussein, a spokesman for Islamabad's main PIMS Hospital, told media. The Brigadier was serving with a UN peacekeeping mission abroad and had returned to Pakistan recently following the death of a relative, PTV reported. Police arrested four suspects, including a teenager, immediately after the attack. Several bullets also hit a vehicle parked at an automobile workshop. Thursdays attack came two days after two suicide bombers struck the International Islamic University in Islamabad, killing six persons and injuring nearly 40 others. Over the past two weeks, Taliban militants have also targeted the UN food agencys office in Islamabad and security facilities across the country, including the armys general headquarters in Rawalpindi.