BAGHDAD - A suicide bomber detonated explosives among a group of men seeking police jobs yesterday, killing 16 people crowded around a recruiting station in northwestern Iraq despite warnings of an attack.

The blast in the town of Sinjar, about 240 miles northwest of Baghdad, occurred about three weeks after U.S. and Iraqi forces launched an offensive to drive al-Qaeda in Iraq out of Mosul, the largest city in northern Iraq and the terrorist movement's last major urban stronghold.

No group claimed responsibility for the blast, but suicide operations are the signature attack of al-Qaeda. The blast could have been aimed at relieving pressure on al-Qaeda fighters in Mosul, 75 miles to the east.

The mayor of Sinjar, Dakhil Qassim, said security services had received tips that police recruiting centers in the area would be targeted. He had issued a warning the day before urging people to stay away from them.

But jobs in the police and army are so prized in parts of the country where unemployment runs high that a large crowd of desperate applicants showed up anyway, hoping to be accepted as recruits, Qassim said.

The dead included 14 would-be recruits and two policemen, Qassim said. An additional 14 people were wounded, he added.

Sinjar is dominated by Yazidis, a small, Kurdish-speaking sect whose members are considered to be blasphemers by Muslim extremists. The U.S. military blamed al-Qaeda for Aug. 14 bombings that devastated nearby villages and killed about 500 people.

Despite continuing attacks, death tolls among civilians and U.S. troops have dropped sharply in Iraq this month. An average of 17 Iraqis had been killed by violence each day in May as of Wednesday, according to an Associated Press tally.

That was the lowest level since December 2005.

At least 20 U.S. troop deaths have been recorded so far this month, putting May on track to have the lowest monthly toll this year, an Associated Press count shows.

Prime Minister Nouri al-Maliki touted his government's security successes and economic progress at a U.N. conference in Stockholm, Sweden.

"Iraq has achieved major success in the battle against terrorism with the support of the international community," Maliki said.

Maliki has called on neighboring countries to forgive debt and compensation payments, saying they are hindering Iraq's road to recovery, despite the drop in violence.

Yesterday, the government announced that Iraq's Shiite vice president had discussed security cooperation with Iranian officials during a previously unannounced visit to Iran, the government said.

Vice President Adel Abdul-Mahdi's visit, which took place during the last two days, was private, the government press office said.

Nevertheless, he met with Iranian President Mahmoud Ahmadinejad, newly elected parliament speaker Ali Larijani and top nuclear negotiator Saeed Jalili to discuss "security matters," the government statement said.

Also yesterday, the head of Iraq's biggest Shiite party declared his opposition to many of the U.S. proposals during ongoing negotiations on a U.S.-Iraq security pact.

Abdul-Aziz al-Hakim said in a statement on his party's Web site that some U.S. proposals "violate Iraq's national sovereignty."

A Day of Attacks Across Iraq

A string of attacks

occurred yesterday against Iraqi security forces, most of which appeared to be the work of al-Qaeda in Iraq.

Gunmen hiding

in a water tanker opened fire on police and pro-U.S. Sunni fighters at a checkpoint in a town near Tikrit, police said. Security forces returned fire, killing a dozen gunmen. The driver of the tanker blew himself up with an explosives belt.

A suicide bomber

driving

a police vehicle blasted Iraqi commandos in

Mosul, killing three troopers and wounding nine other people, according to an officer.

In Baghdad,

assailants hurled grenades at a minibus carrying Iraqi

army recruits, killing two men and wounding five other people, including

a woman nearby.

- Associated Press