BAGHDAD — A suicide bomber blew himself up in a crowd of police recruits on Tuesday, killing at least 52 people and undercutting Iraqi security efforts as the nation struggles to show it can protect itself without foreign help.The death toll was still rising hours after police said the bomber joined hundreds of waiting recruits and detonated his explosives-packed vest outside the police station in Saddam Hussein's hometown of Tikrit, some 80 miles (130 kilometers) north of Baghdad.The attack starkly displayed the Iraqi forces' failure to plug even the most obvious holes in their security as the U.S. military prepares to withdraw from Iraq at the year's end. One recruit who survived the blast said the jobseekers were frisked before they entered the station's yard."We were waiting in the line to enter the police station yard after being searched when a powerful explosion threw me to the ground," said recruit Quteiba Muhsin, whose legs were fractured in the blast. "I saw the dead bodies of two friends who were in the line. I am still in shock because of the explosion and the scene of my two dead friends."Loudspeakers from the city's mosques were calling on people to donate blood for the wounded. An Iraqi television station broadcast footage from the scene that showed pools of blood, bits of clothing and shoes of the victims scattered near a concrete blast wall.Tikrit police put the death toll at 52, with at least 150 wounded. Dr. Anas Abdul-Khaliq of Tikrit hospital confirmed the casualty figures.Tikrit is the capital of Sunni-dominated Salahuddin province, and the city sheltered some of al-Qaida's most fervent support after the 2003 U.S.-led invasion ousted Saddam.Salahuddin provincial councilman Abdullah Jabara accused al-Qaida of being behind the attack."The aim of this terrorist attack carried out by al-Qaida operatives is to shake the security in the province and to bring back instability to Tikrit," Jabara said. "The security forces shoulder responsibility for this tragic incident."Jabara said insurgents successfully exploited what he called "inefficiencies" and "breaches" in security measures, calling it "an indication that the terrorists are still on the job and all security forces should be on high alert all the time."One Tikrit policeman said at least two of the dead were police officers. A second police official said a grenade that had not exploded was found near the scene.The group of recruits was the first to vie for 2,000 new police jobs that Iraq's Interior Ministry recently approved for Salahuddin. They were waiting for interviews and medical checks as part of the application process, police said.Both policemen spoke on condition of anonymity because they were not authorized to release the information.Insurgents have long found recruitment centers a favorite target, taking advantage of lax security measures just outside protective barriers at police stations and the confusion caused by desperate jobseekers scrambling for work in a country with an unemployment rate as high as 30 percent.A similar strike on an Iraqi recruitment center and army headquarters in central Baghdad last August left 61 dead and 125 wounded in what was one of the deadliest attacks of the summer. Two weeks later, militants attacked the same building again, detonating a car bomb and trying to shoot their way in, killing eight and wounding 29.Tuesday's attack was Iraq's deadliest since early November, when a series of bombings on mostly Shiite neighborhoods killed 76 across Baghdad, and followed a weekslong lull that saw mostly small-scale bombings and shootings instead of spectacular violence. It served as a reminder of how unpredictable Iraq's security remains, and that progress can be measured only in small steps.Taxi driver Abdul-Hamid Mikhlaf described the scene in Tikrit as "horrific.""I saw wounded people running in my direction calling for help and asking me to take them to the hospital immediately," he said. "I saw several bodies on the ground as the policemen started to shoot in the air."