BAGHDAD, Iraq, Jan. 9 - Two suicide bombers carrying police identity cards walked up to an Interior Ministry checkpoint on Monday morning and blew themselves up hundreds of yards from a ceremony attended by the American ambassador, killing at least 18 police officers and wounding 25, officials said.
Al Qaeda in Mesopotamia immediately claimed responsibility for the attack, which took place shortly before noon inside a secure zone shared by the city's Police Academy, where the ceremony was being held. Iraq's interior and defense ministers were also at the event, commemorating the formation of the Iraqi Police, but the officials, including the ambassador, were far enough away that the blast did not endanger them.
The bombers, who were wearing suicide vests under plain clothes, were able to walk into an area near the ministry, which is closed to cars, according to a police officer who witnessed the attack. In a troubling lapse of security, the men had obtained police badges and showed them at a checkpoint at the north gate of the ministry.
As the bombers were making their way, they blew themselves up, scattering bodies and shrapnel in all directions.
The blasts were audible at the ceremony, which proceeded uninterrupted, an American military spokesman said. The ceremony took place about a quarter of a mile away.
Still, the apparent ease with which the suicide bombers moved so close to one of the most heavily guarded areas of Baghdad, when senior officials were gathered nearby, underscored how far Iraqis still have to go in their efforts to improve security.
The attacks appeared to be calculated to inflict maximum harm, with the second bomber blowing himself up just as a crowd of policemen gathered to help victims from the first. Reports of casualties varied wildly, with some news agencies putting the death toll at 28.
A relative lull in violence was broken last week when more than 180 Iraqis were killed in a spate of attacks, including one on a mosque and another on a police recruiting center.
The violence comes as Iraq's major ethnic and religious groups are negotiating the shape of a new government. Sunni Arab radicals are responsible for many of the attacks here, and American officials are hoping that broad Sunni participation in a new government will quell them.
Al Qaeda in Mesopotamia seeks to drag Sunnis away from political compromise, and on Sunday, the group's leader, the Jordanian Abu Musab al-Zarqawi, released a statement on the Internet that condemned Iraq's main Sunni party, the Iraqi Islamic Party, for taking part in parliamentary elections in December, according to a translation provided by the SITE Institute, which tracks Islamist Web sites.
Also on Monday, The Christian Science Monitor confirmed the kidnapping of Jill Carroll, a 28-year-old American freelance writer on assignment for the paper. In a statement, it said Ms. Carroll was abducted from a neighborhood in western Baghdad on Saturday morning.
Her interpreter, Allan Enwiyah, 32, was shot dead at the scene. The kidnapping took place less than 300 yards from the office of Adnan al-Dulaimy, a prominent Sunni Arab politician, whom Ms. Carroll had been intending to interview at 10 a.m.
No group has claimed responsibility, and no ransom demand has been made. A spokeswoman for the American Embassy acknowledged only that an American citizen had been abducted and said the American authorities were investigating the disappearance.
At the request of The Monitor, news organizations in Baghdad had agreed to withhold the initial news of her kidnapping while attempts were made to secure her release.
The Monday suicide bombings at the checkpoint were carried out as revenge for what Al Qaeda in Mesopotamia described in an Internet posting as abuses suffered by Sunni Arabs in Interior Ministry prisons, according to the SITE Institute. The posting identified the two Iraqi ministers and the American ambassador, Zalmay Khalilzad, saying the attack was a message intended to show that "their barricaded places will not stop the mujahedeen from reaching them."
But the presence of the senior officials appeared to have prevented greater carnage. The police officer who witnessed the attack said the men had approached him, shown him their passes and said they were going to the contracts department inside the ministry. "I said that we have very important visitors, and we cannot let anyone enter," said the officer, who spoke in an interview from a bed in Kindi Hospital, declining to give his name out of concern for his safety.
One of the bombers was moving about nervously, the officer said, and when a colleague tried to search him, the man took several long steps back, revealing wires underneath his jacket. "My friend told me, run," the officer said.
The police shot at one of the bombers, who blew himself up as they fired, wounding two police officers and killing himself.
The second man became lost in the crowd. Several minutes later, an explosion ripped through the people who had gathered around to help. "I felt myself flying through the air and then smashed on the ground," the officer said, blood on his hand and his legs from shrapnel wounds, his body covered with a blanket.
"My friend shouted to me, 'Please hold me! Please hold me!" the officer said. "I tried to help him. He was very heavy. I lost consciousness."
As of Monday night, he did not know whether his fellow officer had survived.
Among the 18 officers who died were two majors and a colonel, said an Interior Ministry official, who spoke on the condition of anonymity because he is not authorized to speak to the press.
Guests at the Police Day ceremony looked around at the time of the blasts, but the festivities went on without pause. Besides Mr. Khalilzad, Defense Minister Saidoon al-Dulaimy and Interior Minister Bayan Jabr were in attendance.
Imposters among the police and army have struck in suicide attacks before. In Mosul in 2004, a man in an Iraqi Army uniform killed 22 people on an American base, and last year, two Iraqis dressed as police commandos walked into the headquarters of the Wolf Brigade commando unit here and blew themselves up, killing Iraqis.
The Monday bombings came as an American military spokesman confirmed that 8 of the 12 passengers killed in a helicopter crash in northern Iraq on Sunday were American service members. The four others were American civilians, said the spokesman, Lt. Col. Barry Johnson.
The American military also announced the death of a 56-year-old Iraqi man who was a prisoner in the Abu Ghraib prison. The man, who was not identified, died Jan. 7, apparently from complications of a stroke, the military said in a statement.
Qais Mizher, Max Becherer and Dexter Filkins contributed reporting for this article.