Most of the victims of the Thursday blast were recruits lining up outside the station in Hibhib, a town about 14 miles north of Baqouba, a police officer said on condition of anonymity out of security concerns. Baqouba is the capital of Diyala province, which lies northeast of Baghdad.
Fifteen others were wounded in the attack, the officer said.
Two Americans were killed and 10 wounded Tuesday in a mortar or rocket attack, the military said in a statement. It did not release details or the location of the attack, but said the soldiers were assigned to Task Force Marne, which is based on the southern fringes of Baghdad.
Another soldier was killed and two more wounded when a roadside bomb exploded near their vehicle Wednesday during a combat logistics patrol near Basra, in southern Iraq, another statement said. The incident was under investigation, it said.
Military officials reported three deaths on Wednesday as well — three U.S. soldiers on patrol in eastern Baghdad who died Tuesday when they were hit by a sophisticated armor-piercing bomb known as an EFP (explosively-formed penetrator). Six more troops were wounded in the attack.
All six of the victims' names have been withheld pending family notification.
Meanwhile, U.S. officials underestimated how difficult it would be for the Iraqi government to pass political reforms, Defense Secretary Robert Gates said Thursday, adding that the "depth of mistrust" among the factions is greater than anticipated.
Gates comments came as Iraqi prime minister Nouri al-Maliki's party asked the country's largest Sunni Arab bloc Thursday to reconsider its withdrawal from government, in a last-ditch effort to restore Iraq's national unity government.
Talking to reporters on board his plane as he returned from a four-day swing through the Middle East, Gates said he is more optimistic about improvements in security in the wartorn nation than he is about getting legislation passed by the bitterly divided government.
"In some ways we probably all underestimated the depth of the mistrust and how difficult it would be for these guys to come together on legislation," Gates said. "The kinds of legislation they're talking about will establish the framework of Iraq for the future so it's almost like our constitutional convention ... And the difficulty in coming to grips with those, we may all have underestimated six or eight months ago."
Meanwhile, he said security is improving.
"I am optimistic on the security side because of what I see in al Anbar, and what we're seeing in some of the other provinces where we're getting some cooperation," he said.
All six Cabinet ministers from the Iraqi Accordance Front quit al Maliki's regime a day earlier, to protest what they called the prime minister's failure to respond to a set of demands. Among them: the release of security detainees not charged with specific crimes, the disbanding of militias and the participation of all groups represented in the government in dealing with security issues.
Their resignation left only two Sunnis in the 40-member Cabinet, undermining al-Maliki's efforts to pull together rival factions and pass reconciliation laws the U.S. considers benchmarks toward healing the country's deep war wounds.
Al-Maliki's Islamic Dawa Party issued a statement Thursday calling on the Accordance Front to "reconsider its decision."
"The party expresses its concern and regret about this setback for Iraqi politics, an action taken before exploring any dialogue," the statement said.
"We need to stand side by side as a national unity government and set aside all differences and cooperate, in order to answer the challenges our people are suffering," it said.
But an Accordance Front lawmaker, reacting to the Dawa statement, said Thursday that the bloc would reconsider its withdrawal only if promised "the priority of real partnership."
"If we were assured by tangible and concrete promises of real change...and the priority of real partnership, we would reconsider our stance," Salim Abdullah, a Sunni parliament member, told The Associated Press. But he added that he was not optimistic such assurances would come from al-Maliki.
In other developments: