BAGHDAD

- A terrifying wave of bombs tore through mostly Shiite neighborhoods of Baghdad yesterday, killing at least 69 people and evoking fears that Iraq could dissolve into a new round of sectarian violence now that American troops have left.

The attacks appeared to be a well-coordinated assault by Sunni militants linked to al Qaeda and targeted markets, grocery stores, cafes and government buildings in a dozen neighborhoods. They coincided with a government crisis that has already strained ties between the two sects to the breaking point.

For many Iraqis, this could be the beginning of a nightmare scenario: The fragile alliance in the governing coalition is collapsing, large-scale violence bearing the hallmarks of al Qaeda insurgents has returned and Shiite Prime Minister Nouri al-Maliki may be moving to grab the already limited power of the minority Sunnis.

The bombings may be linked more to the withdrawal of the last U.S. troops Sunday than the political crisis, but all together the developments raise the specter of a return to the Shiite-Sunni sectarian bloodshed that pushed Iraq to the brink of civil war in 2006 and 2007.

Al-Maliki is engaged in a showdown with the top Sunni political leader in the country. His government has issued an arrest warrant for Sunni Vice President Tariq al-Hashemi for what al-Hashemi says are trumped-up charges that he ran hit squads against government officials.

That has thrown Iraq's political community into a crisis, with Sunnis suspicious that al-Maliki is making a power grab in the wake of the American departure.

Thrown into this already heated mixture was some of the worst violence Iraq has seen this year.

At least 16 blasts went off across Baghdad, killing 69 people and wounding nearly 200 more. Most exploded in the morning but at least two struck last night

The deadliest attack was in the Karrada neighborhood, where a suicide bomber driving an explosives-laden vehicle blew himself up outside a government office. Two police officers at the scene said the bomber was driving an ambulance and told guards that he needed to get to a nearby hospital. After the guards let him through, he drove to the building and blew himself up, the officers said.

"I was sleeping in my bed when the explosion happened," said 12-year-old Hussain Abbas, standing in his pajamas. "I jumped from my bed and rushed to my mom's lap. I told her I did not want to go to school today. I'm terrified."

In Washington, the White House condemned the bombings and said attempts to derail progress in Iraq will fail. Press secretary Jay Carney said the attacks serve no agenda "other than murder and hatred."

It was exactly this type of violence in the early days after the U.S.-led invasion that eventually spiraled into a near-civil war. Sunni militants such as al Qaeda saw Iraq as their battleground against first the U.S. and then Shiites, whom they do not consider true Muslims.

Shiite militias, fired up by years of repression under Saddam Hussein's Sunni-dominated regime, then fought back in what eventually became a tit-for-tat battle fought mainly across Baghdad.

A bombing against a Shiite neighborhood would be answered by residents of a Sunni neighborhood being dragged out and shot