Back-to-back homicide bombings killed 60 people Friday outside the most important Shiite shrine in Baghdad, a day after the country was rocked by its most deadly violence in more than a year, police officials said.

The latest bombings come amid an increase in high-profile attacks that have raised concerns about the abilities of Iraq's security forces. Such concern led Iraq's prime minister to order a military task force to investigate the attacks as well as security shortcomings that allowed the assailants to slip through.

Nobody immediately claimed responsibility for the bombings, but these types of attacks are the trademark of Sunni insurgents backed by Al Qaeda in Iraq.

The bombers Friday detonated explosives belts within minutes of each other near separate gates of the tomb of prominent Shiite saint Imam Mousa al-Kazim, located in the northern neighborhood of Kazimiyah, said a police official. Another police official said the bombers struck shortly before the start of Friday prayers as worshippers streamed into the mosque — an important site for Shiite pilgrims.

Prime Minister Nouri al-Maliki ordered a military task force to investigate the 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.

Al-Moussawi said the men were being suspended for failing to provide adequate security around the shrine.

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 U.S. military could not provide further 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.

Witnesses at the shrine described a bloody, chaotic scene.

"It is just like a massacre took place," said Laith Ali, 35, who owns a shop near the shrine.

The attack left the bodies of the dead — some of them burned — scattered on the ground near the entrance of the shrine, he said.

"Where are the security precautions that the security officials are talking about?" he said.

Many of the wounded were taken to nearby Kazimiyah Teaching Hospital, overwhelming the staff. AP Television News footage showed many of the injured were forced to wait outside, including women and children, before they could be seen by medical officials.

The 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.

Friday's attack came a day after two bombings in separate areas of Iraq killed more than 80 people.

Violence in Iraq is at its lowest levels since the months following the 2003 U.S.-led invasion. But the recent attacks in Baghdad and elsewhere have exposed gaps in security as Iraq takes over from U.S. forces in protecting the country.

Funerals began Friday for the 88 people killed in the homicide bombings Thursday in Baghdad and in Diyala province.

Coffins were loaded on trucks near the Baghdad offices of the Iraqi Red Crescent, whose volunteers were distributing food parcels in central Baghdad on Thursday when a homicide bomber killed 31 and wounded at least 50 others.

Also Friday, the U.S. 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 U.S. military have died in the Iraq war since it began in March 2003, according to an Associated Press count.