BAGHDAD, Iraq — Sitting in a hospital bed with a leg fractured by shrapnel from a suicide bombing, Iraqi police Sgt. Ali Abdul al-Rahdi said the police had hoped to outwit the insurgency by quietly calling for new recruits to sign up yesterday, a day the country's government offices typically are closed.

The insurgents were not fooled.

A suicide attacker detonated an explosives-laden vest strapped to his body yesterday while standing among a crowd of recruits in central Baghdad. The blast killed at least 20 people, according to hospital officials.

Col. Adnan Abdul-Rahman, a spokesman for Iraq's Interior Ministry, put the death toll at 12 and said 14 others were wounded.

"There was a water tap near the gate where many of the men gathered while they were waiting for the center to be opened," said al-Rahdi, a member of the police's special-commando unit and chief of guards for the recruitment center. "I kept telling the men not to all stand in one area because I worried that someone might attack."

In a statement posted on the Internet, al-Qaida claimed responsibility for the attack.

In a similar attack, a suicide bomber detonated a belt of explosives at a police checkpoint in the mostly Shiite city of Hillah, 60 miles south of Baghdad, police Capt. Muthana Khalid Ali told The Associated Press. The blast killed six police, Ali said.

About 10 minutes later, Ali said, a second suicide attacker blew himself up in a crowd of police and civilians who had rushed to the scene of the first explosion, injuring 26 of them.

Militants also detonated a bomb near a mosque in Mahmoudiya, a city south of Baghdad. Two people were killed and nine others were injured, according to Iraq's Defense Ministry.

Officials at Baghdad's Yarmouk Hospital, which treated many of the casualties, said the bomb was hidden in a vegetable cart in a crowded marketplace. Mourners carrying the coffin of Kamal Ezz al-Deen al-Ghuraifi reportedly were passing through the area when the bomb exploded.

Al-Ghuraifi, an aide to Shiite spiritual leader Ali al-Sistani, was assassinated as he left his mosque Friday. Mourners were carrying his body to the holy city of Najaf, where he was to be buried.

In the northern city of Mosul, a high-ranking police officer was shot to death yesterday morning as he drove to work, an Interior Ministry spokesman said.

Also in Mosul, U.S. troops from the Army's Fort Lewis-based Stryker Brigade detained nine suspected insurgents during raids in the Mosul area of northern Iraq, the U.S. military said.

Soldiers from the 1st Battalion, 24th Infantry Regiment detained seven suspects in a pair of raids in western Mosul late Friday and early yesterday, the statement said. Two more people were detained Friday by soldiers from the 3rd Battalion, 21st Infantry Regiment in northern Mosul, the statement added.

U.S. authorities gave no further details but said "concerned Iraqi citizens" were providing information leading to the detention of insurgent suspects.

U.S. Marine commanders in western Iraq on yesterday announced they were investigating the June 25 death of a cousin of Iraq's ambassador to the United Nations.

Ambassador Samir Sumaidaie charged that U.S.-led forces killed his cousin, Mohammed al-Sumaidaie, 21, during a recent counterinsurgency sweep in western Anbar province, The Associated Press reported. The ambassador said his unarmed cousin was shot without cause when he took Marines into a bedroom to show them where a rifle with no ammunition was kept.

The surge of violence broke a string of relatively peaceful days. While there had been several assassinations of political and Shiite religious figures over the past week, there had been a lull in suicide bombings, which are considered the most precise weapon of the insurgency, until yesterday's attacks in Baghdad and Hillah.

It was at least the third time in the past several months that the recruitment center in Baghdad's Yarmouk district was targeted by suicide attackers or car bombs, al-Rahdi said.

Information on the Stryker Brigade was from The Associated Press.