Iskandariyah, Iraq ? A suicide bomber blew up a truckload of explosives Tuesday outside a police station south of Baghdad, killing at least 53 people and wounding scores — including would-be Iraqi recruits lined up to apply for jobs.

The attack was followed less than a day later by an explosion at an army recruiting center in Baghdad that killed between 20 and 25 Iraqis, a coalition spokesman said.

The 7:40 a.m. blast today in central Baghdad was less than a mile from the Green Zone, the high-security area where the U.S.-led coalition has its headquarters, the spokesman said.

Tuesday’s explosion reduced parts of the station to rubble and damaged nearby buildings.

“It was the day for applying for new recruits,” said policeman Wissam Abdul-Karim, who survived the blast. “There were dozens of them waiting outside the police station.”

The bombing followed warnings from occupation officials that insurgents would step up attacks against Iraqis who work with the U.S.-led coalition. The blast in this predominantly Shiite Muslim city followed the disclosure Monday of a letter from an anti-American operative to al-Qaida’s leadership asking for help in launching attacks against the Shiites to undermine the U.S.-run coalition and the future Iraqi government.

Defense Secretary Donald Rumsfeld told reporters Tuesday in Washington that the attack appeared generally in line with plans outlined in the letter. Attacks on Iraqi security personnel have not deterred more from wanting to join, Rumsfeld said.

But many angry townspeople blamed the Americans for the blast, and some claimed that a U.S. air attack was to blame. “This missile was fired from a U.S. aircraft,” said Hadi Mohy Ali, 60. “The Americans want to tear our unity apart.”

Iraqi police had to fire weapons in the air to disperse dozens of Iraqis who stormed the shattered remains of the station hours after the explosion.