Female suicide bombers struck a Shiite pilgrimage in Baghdad and a Kurdish protest rally in northern Iraq on Monday, killing at least 57 people and wounding nearly 300, police said.

Three women detonated their explosive vests in the middle of pilgrims in Baghdad, moments after a roadside bomb attack, killing at least 32 people and wounding 102, Iraqi officials said.

In the oil-rich northern city of Kirkuk, 25 people were killed and 185 wounded when a blast tore through a crowd of Kurds protesting a draft provincial elections law, officials said.

Police spokesman Brig. Gen. Burhan Tayeb Taha said the bomber was a woman, saying he had seen the remains. The U.S. military confirmed a suicide bombing but said it had no indication the attacker was a woman.

Authorities clamped a 3 p.m.-6 a.m. curfew on the city, which is home to Kurds, Turkomen, Arabs and smaller groups.

The bombings — among the deadliest this year — were a devastating blow to the Iraqi public's growing confidence in recent security gains that have seen violence in Iraq drop to its lowest levels in more than four years.

Such attacks are increasingly carried out by women, who are more easily able to hide explosives under their all-encompassing black Islamic robes, or abayas, and often are not searched at checkpoints.

In a bid to improve the ability to search women, the U.S. military has stepped up recruitment and training efforts for women in the police force and as members of U.S.-allied Sunni groups that have joined forces against al-Qaida in Iraq.

Iraqi security forces deployed about 200 women this week to search female pilgrims near the northern Baghdad neighborhood of Kazimiyah, where the Shiite saint Imam Moussa al-Kadhim is buried in a golden domed shrine.

A senior U.S. military official blamed Al Qaeda in Iraq for the attacks in Baghdad. The attacks come ahead of U.S. and Iraqi military operations in early August aimed at routing out insurgents from rural hideouts in northern Iraq and solidify recent security gains in urban areas.

"At about 8 a.m. three female suicide bombers detonated themselves among pilgrims heading to Kazimiyah," the main Iraqi military spokesman in Baghdad, Brig. Gen. Qassim al-Moussawi, said in a statement posted on his Web site.

The pilgrims are marking the death of an eighth-century saint. The attacks took place in the mainly Shiite Karradah district, which is several miles away from the destination of the pilgrimage in Kazimiyah in northern Baghdad. Most of the dead were women and children, police and health officials said.

"I heard women and children crying and shouting and I saw burned women as dead bodies lied in pools of blood on the street," Mustapha Abdullah, a 32-year-old man who was injured in the stomach and legs, said from the hospital where he was being treated.

It was the deadliest attack in Baghdad since June 17, when a truck bombing killed 63 people in Hurriyah, a neighborhood that saw some of the worst Shiite-Sunni slaughter in 2006.

In Kirkuk, the suicide bomber targeted Kurdish demonstrators who were protesting a provincial elections measure blocked in parliament because of disagreement over a power-sharing formula in the disputed city of Kirkuk, an oil-rich area.

Maj. Gen. Jamal Tahir, a Kirkuk police spokesman, said police found a car bomb nearby and detonated it safely.

After the explosion, dozens of angry Kurds opened fire on the offices of a Turkomen political party, which opposes Kurdish claims on Kirkuk.

A police official, speaking on condition of anonymity because he was not authorized to speak to the media, said no one was hurt in the attack and that the party offices were placed under police protection.

Since the 2003 ouster of Saddam Hussein, who was a Sunni, Shiite political parties have encouraged huge turnouts at religious festivals to display the majority sect's power in Iraq. Sunni religious extremists have often targeted the gatherings to foment sectarian war, but that has not stopped the Shiites.

In 2005, at least 1,000 people also were killed in a bridge stampede caused by rumors of a suicide bomber in Baghdad during the Kazimiyah pilgrimage.