Bombs ripped through an empty apartment building in northern Iraq on Wednesday, killing at least 14 people and injuring as many as 132 in surrounding houses shortly after the Iraqi army arrived to investigate a tip about a weapons cache.

Rescuers were searching for victims buried under the debris of the collapsed building and devastated nearby houses, said Abdul-Karim al-Jubouri, who was heading the operations for police in Mosul, 225 miles northwest of Baghdad.

The cause of the 4:30 p.m. blast was unknown, but it took place after Iraqi soldiers arrived at the three-story building, a suspected bomb-making factory. The army had received calls saying that weapons and explosives were inside, police said.

Al-Jubouri said 14 were killed and the U.S. military said 132 were injured. Al-Jubouri said police do not believe the blast was a trap because insurgents would have waited for security forces to get inside the building to kill as many as possible. Also, he said, insurgents usually warn nearby residents to leave before a bombing.

The blast reinforced claims by the U.S. military several days ago that Mosul is the only major Iraqi city with a strong Al Qaeda presence.

Attacks have persisted in recent months in northern Iraq even as violence has declined in Baghdad and other areas.

In a separate incident, a suicide car bomber targeted a police convoy near the northern city of Kirkuk, killing at least five civilians and injuring 11, police said.

The attacker missed his apparent target — a convoy carrying the head of the area's police academy, Col. Jawdat Hussein, as he patrolled a market in Debis west of Kirkuk, police spokesman Brig. Gen. Sarhat Qadir said. Kirkuk is an oil-rich city 180 miles north of Baghdad

In the capital, Baghdad, gunmen opened fire on Iraqi soldiers resting on the side of a highway, killing three and injuring at least one, according to police and the U.S. military.

The drive-by shooting occurred as the troops were on foot patrol about 11 a.m. in the Bab al-Mudham district on the eastern side of the Tigris River, a police officer said, speaking on condition of anonymity because he was not authorized to release the information.

One of the soldiers, who was wounded in his leg and stomach, said the patrol was near the Finance Ministry when they were attacked. He would only give his first name as Muhsin.

"The highway was almost empty when a speeding white car approached us and the passengers showered us with bullets," he said. "We were taken by surprise and we did not have the time to shoot back."

The attack in the heart of Baghdad provided a deadly example of the stark challenges facing the Iraqi forces as they work to take over their own security so U.S.-led troops can eventually go home. It was the latest in a series of bombings, shootings and mortar attacks as militants seek to undermine recent security gains.

Iraqi politicians and the Shiite-led government of Prime Minister Nouri al-Maliki have been criticized for failing to take advantage of recent security gains to make progress on key U.S.-backed reforms believed necessary to stem support for the Sunni-led insurgency.

With the help of improving Iraqi troops and Awakening Councils — mostly Sunni tribal groups that have turned against Al Qaeda in Iraq — the U.S. military says it has gained command of many key areas across central Iraq.

But it is far more difficult to prevent isolated suicide strikes against less-protected targets.