BAGHDAD -- A suicide bomber driving a truck with explosives hidden under bricks destroyed a police station Saturday in Baghdad -- the largest in a series of insurgent strikes against the American-led security crackdown. At least 47 people died in the attacks, including 20 at the police station.

The bomber bypassed tight security to get within 25 yards of the station by blending in with other trucks coming and going as part of a construction project, detonating his explosives after reaching the main gate. Police said half of those killed were policemen; 28 people were wounded.

"We did not suspect the suicide truck, and he easily reached the main gate where he detonated his truck. Suddenly there was a big explosion and part of the building collapsed," said police Cpl. Hussam Ali, who saw the blast from a nearby guard post. "We were very cautious, but this time we were taken by surprise. The insurgents are inventing new methods to hurt us."

The thunderous explosion caused part of the two-story station to collapse and sent a plume of black smoke drifting across the Baghdad skyline.

U.S. and Iraqi force set up checkpoints at the scene and helped carry the wounded to hospitals, while military helicopters rumbled overhead.

In all, at least 74 people were killed or found dead in Iraq on Saturday, making it the seventh deadliest day since U.S. and Iraqi forces launched the security operation on Feb. 14, according to an Associated Press tally. That included at least 25 bullet-riddled bodies -- 11 found in Baghdad, six pulled from the Tigris River south of the capital and eight in the Anbar city of Fallujah.

The U.S. military also announced the deaths of two more U.S. soldiers on Friday -- one killed by a roadside bomb while on a foot patrol south of Baghdad and another who died in fighting in the Sunni insurgent stronghold of Anbar province.

Northwest of the capital, a man wearing an explosives belt blew himself up outside a pastry shop in a central market area in Tal Afar, killing at least 10 people and wounding three, just over a year after President Bush declared that city was an example of progress made in bringing security to Iraq.

A man driving an explosives-laden truck carrying boxes of new shoes also blew himself up near a Shiite mosque in Haswa, 30 miles south of Baghdad, killing at least 11 people and wounding 45, police said.

Two suicide car bombers also struck a police station in Qaim, near the Syrian border and about 200 miles west of Baghdad. At least six people -- five policemen and a woman -- were killed and 19 wounded in that attack.

The bombings were not as numerous and the casualties not as high as the death tolls that were often in the dozens before the U.S. and Iraqi governments sent thousands more troops to the Baghdad area to try to stop a surge retaliatory attacks between Sunnis and Shiites.

But they came on the heels of a suicide bombing that wounded Iraq's highest-ranking Sunni politician and killed nine other people and a rocket strike that landed near a press conference being held by the U.N. secretary-general in Baghdad, signaling that the Sunni insurgents who usually stage such attacks are picking their targets carefully and finding new ways to overcome security measures.

On March 14, U.S. military spokesman, Maj. Gen. William C. Caldwell, urged patience and cautioned that "high-profile" car bombings, which rose to a high of 77 in February, could "start the whole cycle of violence again."

Since the operation began on Feb. 14, the number of execution-style killings in the capital has declined -- a development officials say is due to an agreement keeping Shiite militias off the street.

U.S. and Iraqi forces, meanwhile, persisted with their neighborhood-to-neighborhood sweep of the capital, stepping up patrols in the Shiite commercial district of Karradah and shelling two mostly Sunni rural districts near the Dora neighborhood -- the scene of several bombardments in recent weeks.

The suicide bomber targeting the police station in central Dora detonated his explosives after being stopped by a long barricade guarded by policemen and surrounded by concrete blast walls, Ali said.

"I was standing near my shop when I heard a big explosion," said 42-year-old Salah Abdul-Wahid, who owns a nearby hardware store. "We rushed to the building to see scattered debris everywhere, fallen blast barriers and bodies and wounded people being taken from the building."

The 10:45 a.m. explosion occurred nearly three hours after two mortar shells landed on a Shiite enclave elsewhere in Dora, killing three people, police said.

Gunmen also ambushed an Iraqi army checkpoint in Baghdad's western Sunni neighborhood of Jami'a, killing a soldier, police said, adding that a militant also was killed in subsequent clashes.

Salam al-Zubaie, one of two deputies to Prime Minister Nouri al-Maliki, meanwhile was moved out of the intensive care unit Saturday morning and was in good condition, Sunni lawmaker Dhafer al-Ani said, adding that the Sunni had received visitors at the U.S.-run hospital in the heavily guarded Green Zone.

The Islamic State in Iraq, an umbrella group that includes al-Qaida in Iraq, claimed responsibility for Friday's bombing against al-Zubaie at a small mosque attached to the politician's home.

Al-Zubaie is among a long list of politicians -- Sunnis, Shiites and Kurds -- who have been targeted by militants seeking to undermine a succession of U.S.-backed governments in Iraq. Close relatives of government officials have also been victims of assassinations, abductions and roadside bombs.