BAGHDAD, Nov. 23 — Last Friday, the Ghazil animal market was a crowded bazaar in a city willing itself into recovery. Cautious but hopeful parents led fun-starved children by the hand to show them parakeets, tropical fish and twittering chicks painted in bright, improbable hues.

As Baghdad’s relative lull in violence had extended from weeks into months, Sunnis and Shiites alike made the calculation — one shared by this correspondent — that Ghazil market was safe enough to risk walking around on a sunny Friday.

It was. But one week later, the market in the shadow of the Mosque of the Caliphs was a scene of carnage, a cruel reminder that the decline in violence in this city is relative and may not last.

Fish tanks lay where they had exploded into the faces peering into them, twisted bird cages were hurled across the street, and human and animal blood was being hosed off the streets by well-practiced firefighters.

When the smoke cleared from Baghdad’s worst bombing in months, the Iraqi police said 13 people were dead and 57 wounded, although the American military put the death toll at 8. Witnesses told the police that two homemade bombs had been hidden inside a bird box, with air holes drilled through its sides.

Ghazil — at least before the Feb. 14 start of the Baghdad security operation that has put thousands more American troops into the capital — had been a regular target.

Operating only on Fridays, it had just begun to recover from a deadly series of attacks. The worst, in January, was identical in execution and scale and killed 15 people. Three died in a mortar attack last December, and four were killed by a twin bombing in June 2006.

Resilient after years of slaughter and reassured by blast walls, Iraqi police checkpoints and decreased car traffic, customers had begun trickling back to one of Baghdad’s most popular attractions in ever-greater numbers.

Last Friday, chatting beside rabbit hutches, their voices sometimes drowned out by the chirping of birds and barking of puppies, shoppers cited the same factors identified by Western journalists to venture out more onto the streets in recent weeks: an increase in American and Iraqi firepower since the Baghdad security plan reached its peak in June; Sunni tribal chiefs’ turning against the shadowy Sunni insurgent group Al Qaeda in Mesopotamia; and a six-month cessation of attacks declared by the Shiite cleric Moktada al-Sadr.

Fathers said they were relieved to get their children out of the house, and fish-sellers laughed. Some even said they were confident that the worst was behind them.

In a sign of changing times, the presence of a visibly Western reporter and photographer fazed no one, a trend apparent in recent months on streets where most were once too scared to be seen talking to foreigners.

As his young son gazed at a cage full of turquoise, yellow and azure-colored birds, Jawad, a 40-year-old car maintenance worker, said he felt safer than before, which is why he gave in to his son’s persistent request to get out of the house.

“We haven’t seen anything good since the end of the war, till now and especially this kid,” he said. “He tells me, ‘We see people taking their kids outside, why don’t we go?’”

Ghazil, for hundreds of years a weavers’ market near the east bank of the Tigris until it became an animal market in recent decades, sprawls across several hundred square yards, covering a major highway and tiny back streets beside the equally ancient spice market.

Dating back to the ancient Islamic Caliphs who gave their name to the nearby Khulafa mosque, it lies within a mixed but mainly Shiite area where posters of Mr. Sadr’s father, Ayatollah Muhammad Sadiq al-Sadr, a revered cleric, adorn shop fronts and the blue-and-white blast walls where the police block cars from entering.

However, the bomber on Friday managed to get past police checkpoints and tight security to sneak the explosives into the market, the blast heard across the city shortly before 9:30 a.m.

“There were many casualties,” said Haidar Ali, 30, a store owner. “I was standing here in my shop, 30 meters away from the explosion. I saw a head resting on the sidewalk, guts and limbs. I just collected guts and put them in a plastic bag.”

Lashing out, some vendors accused the police of failing to check the countless boxes and crates around which customers had clamored for a bargain or a curiosity.

With hindsight, some said the recent lull appeared to have been a tactic by the insurgents, intent on tricking Baghdadis into a false sense of security.

“Last week nothing happened and the week before nothing happened,” said Waad Khalef, 49. “So they let the people feel safe. When they saw the families start to come here, they used this opportunity.”

The American military said such indiscriminate strikes only strengthened Iraqis’ will. “Attacks like this, against innocent Iraqi citizens, are one of the greatest reasons we see the populace making a stand against criminal elements,” said Lt. Col. Scott Bleichwehl, a military spokesman.

Certainly many animal sellers were back plying their trade to willing customers even as the remains of their colleagues and friends were being hosed away.

Yet the mood had changed. Dogs were snarling, and the Iraqi police were jittery.

“We expected such thing to happen despite the security improvement that has been achieved,” said Ali Kadhum, 34, a government employee and resident. “Three months ago, the situation was calm until a bomb attack occurred. I don’t think the situation is becoming better.”

Others were more optimistic. Abdul Salam, 50, a carpenter from Baghdad’s Shaab neighborhood, said he had decided to visit the scene after hearing about the explosion, bringing his young son.

“If we are still afraid, there is no life any more,” he said. “We would have to silently stay at home.”

Mudhafer al-Husaini and Khalid al-Ansary contributed reporting from Baghdad, and an Iraqi reporter for The New York Times from Mosul.

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