Iraqis participate in cleanup at the site of a suicide bombing at a popular pet market Friday in central Baghdad. Two female suicide bomber killed at least 91 people, police said, the deadliest bombing to strike the capital since 30,000 more U.S. troops flooded into central Iraq last spring.

Baghdad ? Two women described as mentally disabled and strapped with remote-control explosives – and possibly used as unwitting suicide bombers – brought carnage Friday to two pet bazaars, killing at least 91 people in the deadliest day since Washington flooded the capital with extra troops last spring.

Brig. Gen. Qassim al-Moussawi, Iraq’s chief military spokesman in Baghdad, said the women had Down syndrome and may not have known they were on suicide missions, but gave no further details on how authorities pieced together the evidence. He also said the bombs were detonated by remote control.

The coordinated blasts – coming 20 minutes apart in different parts of the city – appeared to reinforce U.S. claims that al-Qaida in Iraq may be increasingly desperate and running short of able-bodied men willing or available for such missions.

But they also served as a reminder that Iraqi insurgents are constantly shifting their strategies in attempts to unravel recent security gains around the country. Women have been used in ever greater frequency in suicide attacks because they often encounter less scrutiny by security officials.

The twin attacks at the pet markets, however, could mark a disturbing use of unknowing agents of death.

In Washington, Secretary of State Condoleezza Rice said the bombings prove al-Qaida is “the most brutal and bankrupt of movements” and will strengthen Iraqi resolve to reject terrorism.

Iraqi officials raised the death toll to 91 from 73 in the early hours of today, but they were unable to immediately provide a casualty breakdown in the two bombings. The police and Interior Ministry officials spoke on condition of anonymity because they were not authorized to release the information.

Earlier, officials had said the first bomber was detonated about 10:20 a.m. in the central al-Ghazl market. Four police and hospital officials said at least 46 people were killed and more than 100 wounded.

Police said the woman wearing the bomb sold cream in the mornings at the market and was known to locals as “the crazy lady.”

The pet bazaar has been bombed repeatedly, but with violence declining in the capital, the market had regained popularity as a shopping district and place to stroll on Fridays, the Muslim day of prayer.

But on Friday, it was returned to a scene straight out of the worst days of the conflict. Firefighters scooped up debris scattered among pools of blood, clothing and pigeon carcasses.

About 20 minutes after the first attack, the second female suicide bomber was blown apart in a bird market in a predominantly Shiite area in southeastern Baghdad. Initial reports had said as many as 27 people died and 67 were wounded, police and hospital officials said.

The bombings were the latest in a series that has frayed Iraqi confidence in the permanence of recent security gains.

The U.S. military in Iraqi issued a statement that shared “the outrage of the Iraqi people, and we condemn the brutal enemy responsible for these attacks, which bear the hallmarks of being carried out by al-Qaida in Iraq.”

The U.S. ambassador to Iraq, Ryan Crocker, said the bombings showed that a resilient al-Qaida has “found a different, deadly way” to try to destabilize Iraq.

“There is nothing they won’t do if they think it will work in creating carnage and the political fallout that comes from that,” he told The Associated Press in an interview at the State Department.