Remote-controlled explosives strapped to two mentally handicapped women detonated in a coordinated attack on pet bazaars Friday, police and Iraqi officials said, killing at least 73 people in the deadliest day since the U.S. sent 30,000 extra troops to the capital this spring.

Secretary of State Condoleezza Rice said the use of mentally retarded women as suicide bombers proves al-Qaida is “the most brutal and bankrupt of movements” and will strengthen Iraqi resolve to reject terrorism.

“The struggle is not over and there will be from time to time terrible days like today but I think that will underscore that for the Iraqis and it will make them tougher in the fight,” she told reporters in Washington.

Associated Press records show that since the start of the war at least 151 people have been killed in at least 17 attacks or attempted attacks by female suicide bombers, including Friday's bombings.

Iraqi officials said the women in Friday's attack apparently were mentally disabled and the explosives were detonated by remote control, indicating they may not having been willing attackers in what could be a new method by suspected Sunni insurgents to subvert stepped up security measures.

In the first attack, a woman detonated explosives hidden under her traditional black Islamic robe at about 10:20 a.m. in the central al-Ghazl market. The weekly bazaar has been bombed several times since the war started but recently had re-emerged as a popular place to shop and stroll as Baghdad security improved and a Friday ban on driving was lifted.

Four police and hospital officials said at least 46 people were killed and more than 100 wounded. Firefighters scooped up debris scattered among pools of blood, clothing and pigeon carcasses.

About 20 minutes later, a second female suicide bomber struck a bird market in a predominantly Shiite area in southeastern Baghdad. That blast killed as many as 27 people and wounded 67, according to police and hospital officials.

The attacks were the latest in a series of violent incidents that have been chipping away at Iraqi confidence in the permanence of recent security gains.

Women with Down syndrome selected

The chief Iraqi military spokesman in Baghdad, Brig. Gen. Qassim al-Moussawi, claimed the female bombers apparently had Down syndrome and the explosives were detonated by remote control. Bolstering that claim, local police said the woman in the first attack sold cream in the morning at the market and was known to locals as "the crazy lady."

Iraqi President Jalal Talabani said about 70 people were killed in both attacks, which he said were committed by terrorists motivated by revenge and "to show that they are still able to stop the march of history and of our people toward reconciliation."

Police initially said the bomb at al-Ghazl market was hidden in a box of birds but determined it was a suicide attack after finding the woman's head, an officer said, speaking on condition of anonymity because he wasn't authorized to release the information.

One pigeon vendor said the market had been particularly busy because it was a pleasantly crisp and clear winter day after a recent cold spell.

"I have been going to the pet market with my friend every Friday, selling and buying pigeons," said Ali Ahmed, who was hit by shrapnel in his legs and chest. "It was nice weather today and the market was so crowded."

He said he was worried about his friend, Zaki, who disappeared after the blast about 40 yards away.

"I just remember the horrible scene of the bodies of dead and wounded people mixed with the blood of animals and birds, then I found myself lying in a hospital bed," Ali said.

Fourth female-staged bombing

Navy Cmdr. Scott Rye, a U.S. military spokesman, gave lower casualty figures, saying seven were killed and 23 wounded in the first bombing, and 20 killed and 30 wounded in the second.

He confirmed both attacks were carried out by women wearing explosives vests and said the attacks appeared to be coordinated and likely the work of al-Qaida in Iraq.

At least four other suicide bombings have been staged by women since November, all in the volatile Diyala province northeast of the capital.

The most recent was on Jan. 16 when a female suicide bomber detonated her explosives as Shiites were preparing for a ceremony marking the holiday of Ashoura in a Shiite village near the Diyala provincial capital of Baqouba.

Involving women in fighting violates cultural taboos in Iraq, but the U.S. military has warned that al-Qaida in Iraq is recruiting females and youths to stage suicide attacks because militants are increasingly desperate to thwart stepped-up security measures.

Women in Iraq often wear a black Islamic robe known as an abaya and can avoid thorough searches at checkpoints because men are not allowed to search them and there's a dearth of female guards.

Many teenage boys were among the casualties in the al-Ghazl bombing, according to the officials, who spoke on condition of anonymity because they weren't authorized to release the information.

Unable to stop the bombings

A bomb hidden in a box of small birds also exploded at the al-Ghazl market in late November, killing at least 15 people and wounding dozens. The U.S. military blamed the November attack on Iranian-backed Shiite militants, saying they had hoped al-Qaida in Iraq would be held responsible for the attack so Iraqis would turn to them for protection.

The U.S. military has been unable to stop the suicide bombings despite a steep drop in violence in the past six months, but the explosions on Friday were the deadliest in the capital since Aug. 1, when some 70 people were killed in three attacks, including 50 in a fuel truck explosion in Baghdad.