Gunmen killed three police officers early Wednesday when they burst into a hospital in the northern city of Kirkuk and freed a wounded man who had been arrested for plotting to kill a judge in the Saddam Hussein trial, police said.

Police Brigadier Sarhat Qadir said the attack on Al-Jumhuriya Hospital in Kirkuk, 180 miles north of Baghdad, also injured six police officers.

Police had wounded the suspect when he was arrested with seven other Sunni Arabs on Nov. 26 for allegedly plotting to assassinate the investigating judge, Raed Juhi. The men were carrying a document from former top Saddam deputy Izzat Ibrahim al-Douri ordering them to kill Juhi, police said.

Al-Douri is the highest ranking member of the Saddam regime still at large and is believed to be at least the symbolic leader of Saddam loyalists still fighting U.S. forces and the new government in Iraq.

Juhi's job as investigating judge is to gather evidence and interview witnesses. Once the trial begins, his role in that particular case is finished.

On Tuesday, two suicide bombers detonated explosives inside Baghdad's main police academy, killing at least 43 people and wounding more than 70, police said. Al Qaeda in Iraq claimed responsibility for the attack, the capital's deadliest in months.

The bombing came as Al-Jazeera aired an insurgent video claiming to have kidnapped a U.S. security consultant -- the seventh Westerner abducted in the country since Nov. 26.

Late Tuesday, another suicide bomber blew himself up in a cafe frequented by police in a Shiite neighborhood, killing three people and wounding 20, police said. One of the dead and three of the wounded were policemen, officials said.

The assault on the police academy was carefully planned to maximize casualties, all of whom were police officers or cadets.

The first bomber struck near a group of students outside a classroom, a U.S. military statement said. Thinking they were under mortar fire, survivors rushed to a bunker "where the second bomber detonated his vest," the statement added. One of the wounded was an American contractor.

A statement on an Islamist Web site in the name of Al Qaeda in Iraq said "two blessed brothers" staged the attack on the academy "which continues to produce the dogs that shed the blood and violate the honor of Sunni Muslims."

The claim's authenticity could not be independently verified. But Al Qaeda in Iraq's leader, Abu Musab al-Zarqawi, has often denounced Shiites because of religious differences and their leading role in the U.S.-backed government. Shiites dominate the security services.

Iraqi police also said the attackers may have been policemen or students, fresh evidence that insurgents have infiltrated the country's security forces. President Bush has linked an eventual U.S. troop withdrawal to the ability of Iraq's army and police to combat the insurgents.

The attack was the deadliest against Iraqi security forces since Feb. 28, when a homicide car bomber struck a crowd of mostly Shiite police and army recruits in Hillah, killing 125. In September, at least 88 people were killed in a suicide car bombing in a heavily Shiite neighborhood of Baghdad.

U.S. and Iraqi officials have warned of an increase in insurgent attacks ahead of the Dec. 15 elections. Residents of Ramadireported seeing fliers Tuesday in the name of Al Qaeda in Iraq warning people not to vote and threatening to bomb polling stations.