An onslaught of bombings and shootings killed 93 people across Iraq on Monday, officials said, in the nation's deadliest day so far this year.

The attacks come days after the leader of al-Qaida in Iraq declared a new offensive and warned in a statement that the militant group is reorganizing in areas from which it retreated before U.S. troops left the country last December.

Al-Qaida has been seeking to re-assert its might in the security vacuum left by the departing Americans, seizing on Baghdad's fragmented government and the surge of Sunni rebels in neighboring Syria to sow instability across Iraq.

U.S. and Iraqi officials insist that the terror network's Iraqi wing, known as the Islamic State of Iraq, is nowhere as strong as it was when the nation threatened to fall into civil war between 2006 and 2008, and the Iraqi government is better established.

Still, the huge death toll Monday and an almost-daily drumbeat of killings last month show al-Qaida remains fully capable of creating chaos in the foreseeable future.

Monday's violence in 13 Iraqi cities and towns appeared coordinated: The blasts all took place within a few hours of each other. They struck mostly at security forces and government offices _ two of al-Qaida's favorite targets in Iraq.

"It was a thunderous explosion," said Mohammed Munim, 35, who was working at an Interior Ministry office that issues government ID cards to residents in Baghdad's Shiite Sadr City neighborhood when a car exploded outside. Sixteen people were killed in the single attack.

"The only thing I remember was the smoke and fire, which was everywhere, said Munim from his bed in the emergency room at Sadr City hospital. He was hit by shrapnel in his neck and back.

The worst attack happened in the town of Taji, about 20 kilometers (12 miles) north of the capital. Police said bombs planted around five houses in the Sunni town exploded an hour after dawn, followed by a suicide bomber who detonated his explosives belt in the crowd of police who rushed to help. In all, 41 people were killed, police said.

And in a brazen attack on Iraq's military, three carloads of gunmen pulled up at an army base near the northeast town of town of Udaim and started firing at forces. Thirteen soldiers were killed, and the gunmen escaped before they could be caught, two senior police officials said.

The officials spoke on condition of anonymity because they were not authorized to release the information.

The overall toll made Monday the deadliest day in Iraq since U.S. troops left in mid-December. Before Monday, the deadliest day was Jan. 5, when a wave of bombings targeting Shiites killed 78 people in Baghdad and outside the southern city of Nasiriyah.

Last weekend, the leader of al-Qaida's affiliate in Iraq warned that the militant network is returning to strongholds from which it was driven from while the American military was here.

"The majority of the Sunnis in Iraq support al-Qaida and are waiting for its return," Abu Bakr al-Baghdadi, head of the Islamic State of Iraq since 2010, said in the statement that was posted on a militant website.

Previous al-Qaida offensives have failed to push the country into civil war, largely because Shiite militias in recent years have refused to join in with the kind of tit-for-tat killings that marked Iraq's descent six years ago. Additionally, for all its weaknesses, the Iraqi government now holds more authority than it did during those dark years, and, by and large, citizens have no desire to return down that path.

Still, the militant group appears to be banking on Iraq's fragility in its campaign to throw it into permanent chaos. Sectarian tensions have risen due to a political crisis stemming from terror charges the Shiite-led government has filed against one of the country's vice presidents, who is one of Iraq's top Sunni officials. He says they are politically inspired.

Militant websites appeared to be closely monitoring Monday's attacks, which were hailed by several self-proclaimed jihadists who praised the plan of destruction that al-Baghdadi's statement called "Breaking the Walls."

"Explosions rock Iraq ...The Breaking the Walls plan has come," one poster wrote.

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Associated Press Writer Lara Jakes contributed to this report.