Despondent bird sellers were clearing human flesh, bloodied feathers and the heads of the two women in the deadliest day in the city for at least six months.

The blasts, coming after a marked drop in violence in Baghdad after the infusion of American troops into the capital and a shift by Sunni tribes against the insurgency, left many people here critical of the authorities and pessimistic for the coming year as they fear withdrawals of American troops.

Officials said insurgents had shifted tactics, because increased checkpoints and roadblocks have made it harder to detonate the car bombs that killed much larger numbers of people in the past.

The Iraqi police said the bombs had killed at least 65 people and wounded about 150. The American military, which gave a lower combined death toll of 27, said it suspected the two bombings were the work of Al Qaeda in Mesopotamia, the homegrown Sunni insurgent group that it believes is foreign led.

Iraqi security officials said the women were mentally disabled, but offered no conclusive evidence. The Iraqi officials said the bombs were set off by remote control.

The attacks happened at the hugely popular Ghazil animal bazaar and the smaller New Baghdad bird market. Both markets are in mixed areas of eastern Baghdad and have been attacked numerous times before, the Ghazil market at least five times in the past two years.

The blast at the walled-off Ghazil market, near the Mosque of the Caliphs, exploded shortly after 10 a.m. at exactly the same spot as a Nov. 23 bomb hidden inside a box of birds in which 13 people died. The market was crowded, especially with children and teenagers excited by the brightly hued birds and tropical fish, despite the previous attacks.

The bomb there on Friday killed 38 people, the Iraqi police said. As adults collected scraps of flesh from a nearby roof, children helped pick up the human remains. “Death has become so normal for us,” said one of those children, a boy, 13, who gave his name as Uday. “It doesn’t scare me anymore because I’ve seen a lot up to now.”

About 15 minutes later the second bomb exploded at the New Baghdad bird market four miles away, killing 27 people, the police said. Army units sealed off the market, a parade of dilapidated shops where bloodstained feathers clung to broken cages and shop windows were secured with layers of thick blastproof wiring.

Stall holders there had just received news of the Ghazil bombing. “We were just talking about the first bomb when it happened,” said Abbas Muhammad Awad, 54, a pigeon seller. “There was not enough time for people to leave because it was only 5 or 10 minutes between the bombs. Many kids were killed because children usually gather around the bird sellers.”

Attacks have fallen 60 percent across the country since June.

Ryan C. Crocker, the American ambassador to Iraq, said that Friday’s attacks demonstrated that Al Qaeda in Mesopotamia had “found a different, deadly way” to try to destabilize the country. “Their car bomb capabilities have been badly disrupted so now, as we saw today and as we’ve seen for some time, they are moving toward suicide vests, in this case suicide vests worn by women,” he told The Associated Press in Washington.

Secretary of State Condoleezza Rice said the bombings underlined “the absolute bankruptcy and brutality” of those who carried them out.

At Ghazil, forlorn Iraqis had their own theories. “With these explosions their aim is to make the government look bad and show that the occupation forces did not achieve their main goal of democracy in Iraq,” said Rabaa Hussein, 47, as American Humvees moved back and forth through the market past the Iraqi checkpoint. “If the Americans withdraw it will definitely affect things,” he added. “It would be a disaster for Iraq.”

Hussein Ali, 31, a bird seller who lives near the Ghazil market but moved his stall to Sadr City a year ago because of previous attacks, echoed his pessimism. “It will get worse,” he said, beneath shattered windows and piles of victims’ shoes.

Iraq’s chief military spokesman in Baghdad, Brig. Gen. Qassim al-Moussawi, told The Associated Press that the bombers were mentally impaired.

Other officials made similar claims. Maj. Gen. Abdul Kareem al-Ezzi, a senior officer in the Ministry of Interior police commandos, said officials at the Ghazil market concluded after studying the bomber’s severed head that she had Down syndrome. But Iraqi officials have made similar claims in the past, and it was not immediately clear whether the bomber’s head could have been distorted by the blast.

“We are aware that Iraqi officials have reported the women as mentally disabled,” the American military said in a statement released in Baghdad late on Friday. “We do not have independent reports beyond what they have said, but we have no reason to doubt them.”

One witness, Mohammed Qasem, 35, a vendor at Ghazil, said he saw the woman minutes before the explosion, apparently behaving normally. “She was guiding a small kid with her and she wasn’t uncomfortable at all because she was walking and looking behind her,” he said.

“The child who was with her stopped near me when I saw her for the last time, and a few seconds later the explosion happened and I was thrown a couple of meters away from my booth,” he said. “I recognized her later when I saw the head but the child had vanished, and I want to know what happened to him because I can’t forget the innocent look in his eyes.”

Later, someone covered the bomber’s head with an empty cardboard box of Welcome potato chips.

Abbas Aziz, a member of the Iraqi tribal Awakening movement that helps secure the area, said the bomber appeared to have slipped through because, unlike men, women were not searched at the checkpoint.

“We search every single person coming to the market, especially those who are carrying bags or boxes, but the suicide bomber was a female, whom we don’t search at all,” he said. “We have already learned the lesson.”

American commanders have noted a trend away from car bombings to suicide vests, and the increased use of women as suicide bombers, in areas where checkpoints and roadblocks make it difficult to drive in.

A suicide bomber is “more of a precise delivery tool,” Maj. Gen. Mark P. Hertling, the American commander in northern Iraq, said last month. The tactic, he said, was one way in which Al Qaeda in Mesopotamia was adapting to the proliferation of Iraqi Army, police and Awakening movement checkpoints in Diyala, just north of Baghdad.

“With cars, sometimes you can and sometimes you can’t get them through checkpoints, but you can precisely kill people with suicide vests,” he said. He also noted “an increase in the recruiting of widows of former terrorists to be suicide vest wearers.”

The identity of the women in Friday’s blasts had not been disclosed late on Friday.

Relatives trying to find out if family members had survived created chaotic scenes at Baghdad’s Kindi hospital, which received victims from both bombings. Hundreds of people rushed to the hospital, some mourning when they found victims in the morgue, others frantically searching.

“My husband went to the bird market with my two sons because they love birds a lot, but they haven’t come back yet and I can’t find any of them in here,” said one woman. Ambulances and police trucks were still arriving two hours after the explosion.

At the New Baghdad market, angry stall holders said they had demanded, so far in vain, the same protective blast walls that have been installed in many other vulnerable markets. “I came back to work here because I have to pay rent and I need to support my family,” said Yahya Omran, 50, who is scarred in several places from a previous attack on the market. “I thought everything was starting to get better, but then this happened. I think things are going to get worse.

“It’s chaos.”