TAL AFAR, Iraq – Iraqi police in this provincial backwater got a tip earlier this month that a suicide bomber was on the loose. They were even given his name, age and a description of his car.

With all that, they still couldn't stop him.

Four days after the initial warning, 19-year-old Ashraf al-Yas talked his way through a police checkpoint, drove his vehicle into a crowded farmers market and detonated his explosives. He killed 28 people and injured 72.

The attack raised questions about whether Iraqi forces are yet capable of protecting civilians from determined extremists as across the country, the Americans hand over primary responsibility for security to Iraqi soldiers and police.

The U.S. insists the Iraqi army has made great progress in improving its operational capability. But there are still doubts about efficiency, training and professionalism among police, who must bear primary responsibility for maintaining security in the cities.

U.S. forces only conduct occasional patrols in this northern Iraqi city of 220,000, settled mostly by Turkomen, an ethnic minority divided along religious lines here between Shiite and Sunni Muslims.

Tal Afar's Iraqi army units have been shifted to more troublesome Mosul, a nearby stronghold of Sunni insurgents.

After receiving the initial warning about a suicide bomber, Tal Afar police enforced a vehicle ban to try to keep the assailant off the streets. It's an effective method but can't be imposed for too long without severely disrupting daily life.

In the evening of Aug. 8, police lifted the curfew, and residents crowded the local market.

At one point, a car carrying two men approached the police checkpoint near the market, witnesses say. Hajji Zainel, the local security chief, said police searched the car and allowed it to proceed.

Moments later, the passenger got out, the driver drove into the market and detonated the explosives, witnesses say. It appears the bomber carried a passenger to get around the ban on single men driving alone, imposed to deter lone assailants.

The U.S. military said Iraqi forces should have done a better job of searching at the checkpoints.

But Zainel says he needs more equipment to do the job.

“The main problem we face is a lack of equipment that detects explosives,” said Zainel, adding that only two of the four checkpoints at the city's gates have such devices.

Maj. John Blankenhorn, a U.S. officer in the area, said the U.S. isn't planning to provide equipment to detect explosives, but noted that Tal Afar police have put in requests to the Iraqi government.

On Wednesday, another suicide car bomber struck in Tal Afar, injuring 23 people, the latest in a string of attacks. Tal Afar's deadliest attack was a March 2007 truck bombing that killed 152.

For now, the government is handing out cash to the families of victims.

Last week, a delegation from Baghdad, headed by the deputy prime minister's chief of staff, invited families of those killed or wounded in three recent bombings to the Ottoman-era castle in the center of the city to claim compensation.

They gave out $2,500 for someone killed, and between $845 and $1,270 for someone injured, depending on the length of hospitalization.

The officials checked more than 200 names against lists, as a man from each family collected the money. Sadeq al-Khadr, 25, came for his 13-year-old sister Bushra, who was killed Aug. 8.

Many said it was more important to catch those behind the bombings than to hand out money. Others complained that terror suspects were being released, only to commit more crimes.

Both the Aug. 8 bomber and his alleged accomplice, Fuad Ismail, had been released from prison in Mosul several months earlier. Ismail was freed even though he had killed two men, said Zainel.

“The Iraqi government released him and in fact, they released a lot of people like him,” he said. “The defendants sometimes pay a judge, or bring in a witness and then they go free.”

Ismail, the alleged accomplice, was picked up by police two days after the bombing. Police accused him of planning to attack a Shiite-run hospital in town in a suicide bombing.

Ismail is in Iraqi detention at Tal Afar's castle and denies any role in the car bombing.

For a recent interview, police officers led him blindfolded into a small office. He walked hesitantly, with his hands cuffed behind his back, and appeared dirty and disoriented. After the handcuffs were removed, scars on his wrists were visible, a sign of possible mistreatment.

Ismail denied involvement in the bombing and said he didn't know Ashraf al-Yas.

“They have a witness who said I was with Ashraf Mohammed (al Yas),” he said. “I don't know what is going on. When they captured me, I was surprised.”

The bomber's family, described by Zainel as Islamic fundamentalists, fled to Mosul after the attack, and keeps moving around. Ashraf's father, a well-known school principal in Tal Afar, did not answer his phone.

Sadeq al-Khadr, brother of the 13-year-old girl killed in the market bombing, said he learned through a web of family connections that Ashraf was planning to carry out a suicide attack and that he took the information to the Tal Afar authorities.

Al-Khadr, who has a shop near the market, said he saw Ashraf park his car in the area on the day of the bombing. He said he tried to call police, but couldn't get through, and then witnessed the blast that killed his sister.