BAGHDAD/WASHINGTON: The United States condemned a wave of bombings Thursday that killed at least 72 people in Iraq, while the U.S. Vice President Joe Biden spoke with Iraqi President Jalal Talabani in efforts to calm sectarian tension, the White House said.

“We continue to urge leaders to come together to face common challenges,” White House press secretary Jay Carney said in a statement. “At this difficult time, the United States stands with Iraq as a strategic partner and a close friend.”

The wave of bombings Thursday, the first attacks since Iraq’s Shiite-led government was engulfed in a crisis, risks fracturing the country along sectarian and ethnic lines.

Coming just days after the last U.S. troops left Iraq, the blasts marked a violent backlash against Shiite Prime Minister Nouri al-Maliki’s move to sideline two Sunni rivals.

At least 18 people were killed whena suicide bomber driving an ambulance detonated the vehicle near a government office in Baghdad’s mostly Shiite Karrada district, sending up a huge smoke cloud and scattering car parts into a kindergarten, according to police and health officials.

Police and security sources said there were more than 10 explosions across Baghdad, mostly targeting Shiite districts. A total of 217 people were wounded.

Iraqi officials linked the attacks to the current crisis.

“The timing of these crimes and the places where they were carried out confirm ... the political nature of the targets,” Maliki said in a statement.

A senior U.S. official however said Washington’s initial assessment was that the violence was probably the work of Al-Qaeda.

“It has all the marks of Al-Qaeda, targeting large concentrations of civilians and it could be that they are trying to exploit this by seeking to recreate the support that they had in the west and the north of the country,” the official said, speaking on condition of anonymity.

The last American troops left OPEC oil-producer Iraq over the weekend, nearly nine years after the invasion that toppled Sunni dictator Saddam Hussein.

Upheaval in Iraq would have wider consequences in a region where a crisis in neighboring Syria is taking on a more sectarian tone, and Shiite Iran, Turkey and Sunni Arab Gulf nations are jostling for influence.

In the other Baghdad attacks, two roadside bombs struck the southwestern Amil district, killing at least seven people and wounding 21 others, while a car bomb blew up in a Shiite neighborhood in Doura in the south, killing three people and wounding six, police said.

More bombs ripped into the central Alawi area, Shaab and Shula in the north, all mainly Shiite areas, and a roadside bomb killed one and wounded five near the Sunni neighborhood of Adhamiya, police said.

An old woman wrapped in black yelled and called out for her husband, lost under the rubble, after two bombs struck a wholesale vegetable market where they both worked.

“I cannot find my husband, I don’t know if they took him out or not, I don’t know,” she said.

Just days after the U.S. withdrawal, Iraq’s fragile power-sharing government is grappling with its worst turmoil since its formation a year ago. Shiite, Sunni and Kurdish blocs share out government posts in a unwieldy system that has been impaired by political infighting since it began.

This week, Maliki called for the arrest of Sunni Vice President Tareq al-Hashemi on charges he organized assassinations and bombings, and he asked parliament to fire his Sunni deputy Saleh al-Mutlaq after he likened Maliki to Saddam.