Residents emerged from their homes Sunday at the end of a four-day lockdown and found themselves caught in traffic spawned by hundreds of new police and army checkpoints.

Many wondered if the extra security and the curfew imposed after last week's bombing of a major Shiite shrine had only created inconvenience and delayed an inevitable explosion of revenge attacks.

"The militias will still take revenge, today or tomorrow," said agricultural materials merchant Nasser Ali Jaber, a 56-year-old Shiite father of three.

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The bombing of the Askariya shrine north of Baghdad was the second there in 16 months. The first, which destroyed the glistening golden dome, unleashed a torrent of Shiite-Sunni violence that continues to this day.

As the Baghdad curfew ended, the U.S. military reported it killed 14 suspected insurgents and captured 20 others in separate operations over the weekend. At least 37 other people were killed or found dead in sectarian violence Sunday.

Three U.S. soldiers were killed Saturday in explosions near their vehicles — two in Baghdad and one in Kirkuk province, the U.S. military reported. The deaths raised to 3,524 the number of U.S. service members who have died since the war began, according to an Associated Press count.

One mosque was known to have been attacked in Baghdad and several were targeted south of Baghdad, including a major Sunni shrine that was leveled by an explosion outside Basra, Iraq's second city. There was no repeat of the wholesale attacks on Sunni mosques and clerics that took place after last year's bombing.

But the ban on vehicle traffic and large gatherings led to steep price hikes for fuel, and fresh food as well as longer power outages than normal because people were forced to remain home, putting an additional burden on the power grid. Baghdad is routinely off the central grid for as long as 20 hours a day.

Sunday saw some of the longest gas lines since Iraqis began suffering what are now chronic shortages. The lines stretched for a mile or longer, in some cases weaving around several blocks, stretching from main roads deep into side streets.

Black marketeers, some of them boys as young as 10, positioned their jerry cans of gas near the lines, charging three times the pump price.

Residents complained they had run out of fuel to power generators, and fresh food, and said merchants were price-gouging.

For Mona Abdul-Hussein, a 32-year-old engineering lecturer and mother of two, little came from the lockdown aside from higher food prices and longer power outages.

"I think things will get worse now," she said of a possible outburst in sectarian violence. "Anyone who wanted to do this may have just delayed until after the curfew."

The end of the lockdown came a day after Lt. Gen. Raymond Odierno, a top U.S. commander in Iraq, acknowledged that security forces have full control of only 40 percent of Baghdad, now in the fifth month of a major U.S.-led security push that may be the U.S. military's last.

Except for street sweepers hard at work in bright orange or yellow vests, and municipal workers watering trees, the city of some six million people was tense Sunday, with greatly stepped-up security.

Vendors weaved between cars waiting in traffic, selling paper fans, soft drinks and tissues to mop brows dripping in temperatures that hit 112.

Feeding the tension in a city that has been on edge for much of the past four years, army and police commandos raced through the capital's streets in pickup trucks mounted with machine guns, with sirens blaring and headlights flashing.

To great relief, they have followed government orders to stop shooting in the air to clear traffic or warn motorists coming too close.

Security was particularly tight on bridges, with Iraqi police and soldiers searching trucks for bombs. Several bridges, which link the mainly Sunni Karkh region on the west bank of the Tigris river to the Shiite-dominated Rusafa area on the opposite side, have been targeted by suspected Sunni militants.

In some areas of Karkh, where militants from al-Qaida and other Sunni groups are active, checkpoints were just 100 yards or less apart. In districts that insurgents often target — like Mansour and Yarmouk — Iraqi army soldiers took cover behind concrete blast barriers.

The government ordered higher security for mosques in Baghdad to head off reprisal attacks after Wednesday's bombing, but there was no sign of unusual security outside Abdul-Qader al-Jilani mosque, one of Iraq's holiest Sunni sites and the target of a recent bombing. There was no sign of any security outside another major Sunni mosque, al-Nidaa in north Baghdad.

Al-Jilani mosque is located in a small Sunni quarter surrounded by Shiite neighborhoods where the Mahdi Army militia, blamed for much of the sectarian violence, is active.

In Azamiyah, a Sunni stronghold in northern Baghdad where insurgents hold sway, Iraqi troops in combat gear patrolled the streets in armored cars. Soviet-era tanks were stationed on major roads and intersections. Much of Azamiyah was almost deserted, with most stores shuttered and little traffic on the streets.

Ironically, Azamiyah's Shiite enclave of Kasrah was buzzing with shoppers in open-air markets. Kebab stands were doing a big business. The streets in the mainly Shiite Karradah district in central Baghdad appeared back to normal as well. Traffic was heavy, shops open.

The two areas could have been what the top American commander in Iraq, Gen. David Petraeus, had in mind when he said last week that there were "astonishing signs of normalcy" in the city.

Many parts of Karkh, for example, were deserted, with stores shuttered and barbed wire or tree trunks blocking access to residential side roads. Row after row of houses seem abandoned and, in some parts, snipers fired randomly at pedestrians and cars.

"Other solutions other than curfews must be found," said Saleh al-Khafaji as he sat inside the baking cab of his truck in Karradah. "The curfew did not stop the violence. There was mortar shelling every day of the curfew," said the 52-year-old father of four.

Complete coverage is available in FOXNews.com's Iraq Center.