BAGHDAD (AP) – Iraqi authorities ordered a one-day vehicle ban in the volatile city of Baqouba on Friday in the wake of a series of deadly suicide bombings and other attacks by al-Qaeda in Iraq against predominantly Sunni fighters that have allied with the United States.

The ban also comes as the U.S. military stepped up operations against al-Qaeda cells and networks in Diyala province, of which Baqouba is the capital.

The U.S. military announced it had killed a senior al-Qaeda in Iraq leader, Muhammad Khalil Ibrahim, during a Dec. 28 airstrike in Mahmoudiya, about 30 kilometers (20 miles) south of Baghdad, in an area known as the “Triangle of Death” just south of Baghdad. It identified Ibrahim as “the deputy military leader for the al-Qaeda in Iraq network operating south of Baghdad.”

Baqouba police chief Brigadier Hasan al Obaidi said the ban was imposed because of the “increased violent events during last week.” The ban in the city located 60 kilometers (35 miles) northeast of Baghdad also aimed to protect worshippers going to mosques for Friday prayers. It was to last until late afternoon. “Imposing the vehicle ban is a decision taken by the governor and provincial security officials based on security developments,” he said.

There have been a series of suicide attacks targeting members of the burgeoning Sunni tribal movement, including one attack in downtown Baqouba on Wednesday that police said killed seven people; the U.S. military said four people died.

The attacks intensified after a Dec. 29 message from Osama bin Laden warning Iraq’s Sunni Arabs against joining the U.S.-funded groups fighting al-Qaeda.

The overwhelmingly Sunni groups have since become the targets of a series of deadly attacks. They are known as Awakening Councils in some areas, and as Concerned Local Citizens by the U.S. military in others. Iraqis used the general term “Sahwa,” or awakening, to describe all of them. There are more than 70,000 men in about 300 such groups being bankrolled by the U.S. around Iraq, and the number is expected to grow.

The groups have been credited with playing an important role in reducing violence by 60 percent around the country in the past six months.

They have also helped push al-Qaeda out of Anbar province, just as the inflow of thousands of U.S. troops pushed insurgents north of Baghdad. The great bulk is thought to have sought shelter in the northeast Diyala river valley region and around the town of Muqdadiyah.

The U.S. military said Friday it had killed two insurgents and detained another 12 in that area. But the operations also resulted in the deaths of two American soldiers the wounding of another in a small arms attack on Thursday in Diyala, the military said.

One of those captured by the military included an alleged leader of Ansar al-Sunna, a terror group affiliated with al-Qaeda. It did not identify him by name.

“The wanted individual is allegedly responsible for numerous attacks against Coalition forces. Reports also indicate the suspect was previously injured during an Iraq forces operation, and he allegedly escaped from the hospital with the help of other terrorists, killing five Iraqi policemen during the escape,” the military said in a statement issued in Baghdad.

But the groups have also worried the Shiite-dominated government, which has been deeply uneasy about the potential for the Sunni fighters to switch sides again. One such tension point has been Baghdad’s Sunni neighborhood of Azamiyah, where fighting broke out Wednesday and Thursday between one such group led by Abu Abed and Iraqi security forces.

Abed, who leads the biggest group in Azamiyah, told The Associated Press that the U.S. military had for the time being accepted a demand that Iraqi security forces withdraw from the inner part of the neighborhood to Antar Square on its edge.

“We insist that security in the district should be handed over to the awakening and that no soldier of the (Iraqi) national guard should be in the district streets or alleys,” he said.

The U.S. military wants the groups to eventually be integrated, with about a quarter joining the Iraqi security forces and the rest entering the civilian work force.