A suicide bomber driving a truck with explosives hidden under a load of bricks destroyed a police station Saturday in south Baghdad - the largest in a series of bombings that killed at least 40 people as insurgents step up high-profile attacks in an apparent bid to derail the American-led security crackdown in the capital. The attacker bypassed tight security to get within 25 meters 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 20 people were killed, half of them policemen, and 28 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 witnessed 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. US and Iraqi force set up checkpoints at the scene and helped carry the wounded to hospitals, while military helicopters rumbled overhead. 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 US President George W. Bush declared that city was an example of progress made in bringing security to Iraq. A parked truck also exploded near a Shi'ite mosque in Haswa, 50 kilometers south of Baghdad, killing at least 10 people and wounding nearly 40, police said. The bombings were not as numerous and the casualties not as high as the death tolls that were often in the dozens before the US and Iraqi governments sent thousands more troops to the Baghdad area as part of a security sweep to try to stop a surge retaliatory attacks between Sunnis and Shi'ites. But they came on the heels of a suicide bombing that seriously 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 UN secretary-general in Baghdad, signaling that the Sunni insurgents who usually stage such attacks are picking their targets carefully and finding new ways to get around the stepped up security measures. In all, at least 68 people were killed or found dead in Iraq on Saturday, making it the ninth deadliest day since US and Iraqi forces launched the security operation, 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 US military also announced the deaths of two more US 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. US and Iraqi forces, meanwhile, persisted with their neighborhood-to-neighborhood sweep of the capital, stepping up patrols in the Shi'ite commercial district of Karradah and shelling two mostly Sunni rural districts near the Dora neighborhood - the scene of several bombardments in recent weeks. 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 US-run hospital in the heavily guarded Green Zone.