BAGHDAD, Iraq (AP) -- Insurgents killed at least 20 people in three separate attacks targeting Iraqi security forces in Baghdad on Thursday, including one by a man who set off hidden explosives while waiting in line outside an army recruitment center, police said.

A similar attack Wednesday by a suicide bomber standing in a line outside a police recruitment center in the northern Kurdish city of Irbil killed 60 and wounded 150.

The attacks are part of an escalation of violence aimed at destabilizing Iraq's new democratic government. The insurgents often target Iraqi security forces, which are being recruited and trained by the U.S.-led coalition as part of its eventual exit strategy.

In the deadliest attack Thursday, a man carrying hidden explosives set them off while standing in a long line of job applicants outside an Iraqi army recruitment office in central Baghdad, killing at least 11 people, police and hospital officials said. At least six people were wounded in the 8 a.m. attack, a police officer said on condition of anonymity.

The recruitment center, which has been hit by insurgent attacks before, is surrounded by a cement wall topped with barbed wire. It is located on the site of a former Iraqi army airfield.

''While we were standing in a line, a man walked past, right up to the heavily guarded entrance gate, as if he wanted to ask the guards a question,'' said Anwar Wasfi, who was standing toward the end of the line of recruits.

''Suddenly, an explosion occurred, and I was knocked over,'' Wasfi said during an interview at Yarmuq Hospital, where he was being treated for leg and arm wounds.

The U.S. military said it could not immediately confirm the attack, which was reported to be less than a half mile from the Green Zone, where Iraq's parliament and embassies are located and heavily protected by American forces.

In western Baghdad on Thursday, insurgents attacked two police patrols, killing a total of nine policemen, an official said.

Gunmen opened fire on a patrol in the Al-Amil area of western Baghdad at 6:45 a.m., killing eight policemen and wounding two, said police Maj. Mousa Abdul Karim.

About 15 minutes after the Al-Amil attack, a suicide car bomb exploded in the nearby Al-Gazaliya area, killing one policeman, wounding six and destroying four of their cars, said Karim.

The U.S. military said it had no immediate information about attacks in Al-Amil or Al-Gazaliya.

A car bomb also exploded Thursday morning near a police station in Baghdad's southern neighborhood of Dora, but no casualties were immediately reported, said police Capt. Talib Thamir.

A suicide car bomber attacked an Iraqi army checkpoint in the same area late Wednesday, killing at least nine soldiers and wounding 16, including 10 civilians, police said. The U.S. military said as many as 15 soldiers were killed but just six wounded.

Wednesday's brutal attack in Irbil, 215 miles north of Baghdad, was the deadliest one in Iraq since Feb. 28, when a suicide car bomber struck a crowd of police and national guard recruits in Hillah, south of Iraq's capital, killing 125 and wounding more than 140.

The Irbil tragedy left pieces of flesh spattered on the walls outside the police recruitment center. Nails and shards of metal were packed in with the explosives to maximize casualties.

A Sunni militant group, Ansar al-Sunnah Army, claimed responsibility, saying the attack was revenge for Kurdish cooperation with U.S. forces.

Some 250 job seekers were waiting to be searched outside the recruitment center when the bomb went off, said police Capt. Othman Aziz. An Iraqi insurgent joined the line and detonated explosives concealed on his body, he said.

Panicked relatives crowded into the Irbil Teaching Hospital, where staff used loudspeakers to announce victims' names and room numbers. Women squatted on the ground wailing and beating their chests.

''Oh God, what did we do wrong?'' Horras Mohammed Amin screamed from his hospital bed, his face and leg bloodied from the attack.

The 25-year-old was standing near the end of the line when the blast threw him into the street. ''I wanted to find a job because it is very shameful for a young man like me to take money from his father,'' he said.

The U.S. military put the toll at 60 dead and 150 wounded in the attack. More than 200 people have been killed in insurgent violence across Iraq since the new government was announced last week.

Attacks against security forces have become so frequent in Baghdad and other major centers that most recruitment centers are surrounded by protective blast walls. But the northern Kurdish areas usually have been spared the worst of the violence, in part because members of the Sunni Arab minority believed to be driving the insurgency stand out and are closely watched.

Ansar al-Sunnah, in its statement posted on a militant Web site, claimed the attack was a car bombing and said it was staged to punish Kurdish security forces that have ''bowed their heads to the Crusaders and raised their spears against the Muslims and fought alongside the Americans.'' There was no bomb crater in the street, as there normally would be after a car bombing.

Ansar al-Sunnah is believed to be a breakaway faction of Ansar al-Islam, a Kurdish-led group with links to al-Qaida. It has claimed responsibility for numerous attacks against Iraqi security forces and twin suicide bombings targeting Kurds in Irbil that killed 109 people in 2004.

Insurgents have stepped up their attacks since a new Cabinet was approved last week.

Prime Minister Ibrahim al-Jaafari hoped to include members of the Sunni minority, which dominated under Saddam Hussein, in his government. But members of his Shiite-dominated alliance have blocked candidates with links to Saddam's regime, which brutally repressed Shiites and Kurds.

After months of wrangling, the 37-member Cabinet included just four Sunni ministers in relatively minor posts. Bickering continues over seven positions, including the oil and defense ministries, which remain in temporary hands.