Two suicide bombers killed 60 people outside a heavily guarded Shiite shrine in Baghdad on Friday, prompting Iraq's prime minister to order an investigation into security shortcomings that allowed the assailants to slip through. Violence in Iraq has dropped to its lowest levels since the months following the 2003 US-led invasion, but an increase in suicide bombings and other devastating attacks in recent weeks has renewed concerns about the capabilities of Iraq's security forces. Prime Minister Nouri al-Maliki suspended the commanders who oversaw security in the northern Baghdad neighborhood of Kazimiyah, where Friday's attack took place. The bombers detonated explosive belts within minutes of each other near separate gates of the tomb of the Shiite saint Imam Mousa al-Kazim, said a police official. Another official said the bombers struck shortly before the start of Friday prayers as worshippers streamed into the mosque - an important site for Shiite pilgrims. Laith Ali, 35, who owns a shop near the shrine, said security at the time of the bombing was high. "We felt secure because security checks were going on at the main entrances to the shrine," he said, adding that both men and women were being checked. The blasts left the dead - some of their bodies burned - scattered near the entrances, witnesses said. Hours later, pools of blood still streaked the sidewalks. Among the dead were 25 Iranian pilgrims, said a police and a hospital official. Both said at least 125 people, including 80 Iranian pilgrims, were injured in the blast. The US military could not provide details, saying the area around the shrine was patrolled by Iraqi security forces. All the officials spoke on condition of anonymity because they were not authorized to release the information. Staff at the nearby Kazimiyah Teaching Hospital were overwhelmed trying to treat the injured. AP Television News footage showed many of the wounded - including women and children - were forced to wait outside the hospital before they could be seen by medical staff. A day earlier, two suicide bombings in different parts of the country killed 88 people. Iraq's leadership is trying to ensure that its security forces will be able to keep Iraqis safe as the United States prepares to withdraw its troops. Al-Maliki ordered a military task force to investigate Friday's bombings and ordered the battalion and company commanders responsible for security in the area to be relieved of duty during the investigation, said military spokesman Maj. Gen. Qassim al-Moussawi. The men were being suspended for failing to provide adequate security around the shrine, al-Moussawi said. President Barack Obama has announced plans to withdraw American combat troops from Iraq by Aug. 31, 2010, leaving 30,000 to 50,000 troops in training and advisory roles. Under a US-Iraqi security pact, those remaining American troops would be withdrawn by the end of 2011. Nobody claimed responsibility for Friday's bombings, but these types of attacks are the trademark of Sunni insurgents backed by al-Qaida in Iraq. The Baghdad shrine has been a favored target of insurgents, most recently in early April when a bomb left in a plastic bag near the shrine killed seven people and wounded 23. In January, a man dressed as a woman blew himself up near the shrine, killing more than three dozen people and wounding more than 70. Imam Mousa al-Kazim is an eighth century saint and one of 12 Shiite saints. Hundreds of thousands of Shiites march to the shrine in Kazimiyah every year to commemorate his death in A.D. 799. Shiites believe al-Kazim is buried in the Baghdad golden-domed shrine. Also Friday, the US military said an American soldier died as a result of a noncombat related incident in the northern Salahuddin province. At least 4,277 members of the US military have died in the Iraq war since it began in March 2003, according to an Associated Press count.