BAGHDAD, Feb 11 -- At least 12 people were killed Sunday after a bomb detonated in front of a police station near Tikrit, a police spokesman said.

Capt. Muthana al-Duri said a suicide bomber drove a KIA pick-up truck to the police station in the town of Dour Sunday morning. The blast injured several students at a school across the street from the police station and damaged a few houses.

One police officer injured in the blast said the explosion slammed him against the wall. "I was inside the police station and only realized that there was a loud explosion which I could not describe, for I have not heard anything like that before in my life," said the officer, Ahmed Subhi, 23. "I was holding a tray with tea cups and the last thing I remember was that I was being pushed along with the tray towards one of the walls in the room and parts of the ceiling falling on me."

Earlier reports Sunday morning had said the suicide truck bomber had killed at least 30 people, injuring about 50. Also on Sunday, witnesses said a U.S. Apache helicopter had been shot down near Taji, about 12 miles north of Baghdad, according to wire services, but a U.S. military spokeswoman said the military had no reports of a helicopter going down.

A U.S. soldier was killed yesteday after coming under small-arms fire in Diyala province northeast of Baghdad, the U.S. military said, correcting its earlier report of the casualty occurring today. Coalition forces were conducting combat operations when they came under fire, the military said. The name of the soldier was being withheld until the soldier's family could be notified.

In the Mansour neighborhood of Baghdad, a parked car bomb exploded today, killing two people and wounding three, wire services reported.

The continuing violence came the day after Gen. David H. Petraeus took charge of U.S. forces in Iraq, more than 130,000 troops, saying that the challenges facing Iraq are daunting but "these tasks are achievable, this mission is doable."

The U.S. military said today that Iraqi security forces and U.S. soldiers uncovered 14 weapons caches and detained 140 suspected insurgents in and around Baghdad this pas week.

Brig. Gen. John Campbell, deputy commander of U.S. forces in Baghdad, said nearly 3,800 of the more than 7,400 patrols conducted during the week were conducted by Iraqi forces.

Campbell said elements of the 82nd Airborne Division's 2nd Brigade Combat Team and Iraqi security forces established a combat outpost in the Adhamiyah district of the capital.

"These joint combat outposts allow Iraqi security forces and coalition troops the ability to reach out within these neighborhoods, providing a steadying presence and allowing them to understand the security and safety concerns of the residents, firsthand," Campbell said. "Just having us there, 24 hours a day, seven days a week, will improve the security situations within these areas."

Campbell said he's encouraged by the early results of the new security plan for Baghdad. "With the cache finds this week, the detentions we've made and creating a larger presence on Baghdad streets with the establishment of another combat outpost, we are making headway with the Baghdad security plan," Campbell said. "This is only the beginning."

Sarasohn reported from Washington.