Car bombs killed 10 people in Baghdad on Thursday as violence persisted in the capital despite the U.S.-led security crackdown. Two more American soldiers were killed in combat, the U.S. command said.

Iraqi officials announced plans to double the amount of money spent to import fuel to combat the country's worst oil and gasoline shortages in years. Much of the fuel crisis is due to insurgent attacks on convoys and on Iraq's fragile pipeline network, Oil Ministry officials said.

Seven people were killed and 15 were wounded when a car bomb exploded at midday near an outdoor market in Sadr City, Baghdad's biggest Shiite district, the Iraqi army general command said.

The blast wrecked shops and stalls but caused relatively few casualties in the normally crowded area because many people had left the area to escape the 120 degree midday heat.

CountryWatch: Iraq

Another car bomb missed an Iraqi police patrol in the Mansour district of western Baghdad but killed three bystanders and wounded a fourth, police Capt. Jamil Hussein said.

The two American fatalities included one soldier killed Thursday when a roadside bomb exploded near a foot patrol south of Baghdad, the U.S. military said. The other was a soldier from the 1st Brigade, 1st Armored Division who died Wednesday of wounds suffered in Anbar province, stronghold of the Sunni Arab insurgency west of Baghdad.

This month, at least 26 U.S. service members have died in Iraq — 17 of them in Anbar.

The Baghdad bombings occurred in areas of the city not yet targeted in a new U.S.-led security crackdown, which began this month with the arrival of thousands of U.S. and Iraqi reinforcements.

Those troops will try to quell Sunni-Shiite violence that has brought the country to the brink of civil war. The operation has focused on four Baghdad neighborhoods — three mostly Sunni areas and one that is predominantly Shiite.

U.S. and Iraqi troops plan to expand to other parts of the city in a campaign to restore order neighborhood by neighborhood. The interior minister announced a partial curfew in unspecified Baghdad neighborhoods this weekend, when hundreds of thousands of Shiites turn out for ceremonies marking the death of Imam Musa Kadhim, an 8th-century Shiite saint.

The security operation follows one of the most violent months since the war began in March 2003. Much of the recent violence was reprisal kidnappings and killings by Sunni and Shiite extremists.

On Thursday, however, U.S. officials confirmed that the number of roadside bombs directed against American and Iraqi forces increased sharply in July, dramatizing the threat still posed by the Sunni-led insurgency.

U.S. officials said that in July, 2,625 bombs exploded or were discovered before they could detonate. That was up sharply 1,454 bombs in January.

Of the bombs discovered in July, 1,666 of them exploded and the rest were detected. About 70 percent of them were directed at U.S.-led forces, 20 percent at Iraqi security forces and 10 percent against civilians, the officials said. They spoke on condition of anonymity because they were not authorized to release the figures.

The figures suggest that the Sunni Arab insurgency is gaining strength despite setbacks, including the June 7 death of Al Qaeda in Iraq leader Abu Musab al-Zarqawi, killed in a U.S. airstrike northeast of Baghdad.

Deputy Health Minister Adel Muhsin said Wednesday that about 3,500 Iraqis died in July in sectarian or political violence nationwide, the highest monthly toll for civilians since the war started.

The spike in violence has dealt a devastating blow to fuel supplies because of attacks on convoys and Iraq's pipeline system. Gasoline and other petroleum products are in short supply in Baghdad, adding to the suffering of Iraqis weary of killings, kidnappings and soaring crime.

A gallon of gasoline now sells on the black market in Baghdad for about $4.92, although the official price is 64 cents a gallon. Lines of cars at many Baghdad fuel stations stretch for several miles, and drivers sometime wait overnight to fill up their cars.

Falah Alamri, head of the State Oil Marketing Organization, said the money normally allocated by the government to buy oil products was doubled in August, to $426 million. The amount allocated for September also will be doubled, Alamri told Dow Jones Newswires.

Alamri blamed the fuel shortage on the shutdown of the Beiji refinery north of Baghdad, which produces 140,000 barrels daily. Sabotage of pipelines carrying crude from Kirkuk oil fields in the north shut down the refinery for the last four weeks, he said. It has now resumed operations.

Iraq's three main oil refineries — Dora, Beiji and Shuaiba — are working at half capacity, processing only 350,000 barrels per day compared to 700,000 barrels a day before the war.