A suicide bomber slammed his truck into a densely populated residential area in the northern Iraqi city of Tal Afar on Monday, killing at least 28 people, including 19 children, local authorities said. The attack occurred in a crowded Shiite neighborhood of the religiously mixed city, 420 kilometers northwest of Baghdad. The powerful blast caused houses to collapse in the morning as many families were getting ready for the day ahead, and officials said the death toll could rise. Many of the casualties were women and children, officials said. "Rescue teams are still searching for casualties among the rubble," said Ali Abbo, the head of the human rights committee. He said the hospital in Tal Afar had been filled to capacity, forcing the ambulances to take many victims to Dahuk, about 70 kilometers to the north. The attacker drove a dump truck filled with explosives and covered with a layer of gravel, Brig. Gen. Najim Abdullah said, adding that at least 19 children were among the 28 killed. At least 40 people were wounded in the attack, said Brig. Gen. Rahim al-Jibouri, commander of Tal Afar police. Several residents said the area is heavily populated, with four families sharing one house in some cases, and several boys and girls were playing hopscotch and marbles outside the houses at the time of the explosion. Authorities imposed a complete curfew on the city, officials said. Sheik Mohammed Qassim, 52, said the explosion shifted the furniture in his house and smashed all his windows. "We rushed outside to see a big cloud of dust and smoke and shrapnel covering the street," he said, adding a 3-meter was left in the street. He and his neighbors didn't wait for emergency crews to arrive but began searching for survivors in the rubble with their own hands. In Baghdad, Iraqi authorities girded for a major Shiite pilgrimage later this week to commemorate the eighth century death of Imam Moussa ibn Jaafar al-Kadhim, one of the 12 principal Shiite saints who is buried in a mosque in the northern neighborhood of Kazimiyah. The procession was struck by tragedy in 2005, when thousands of Shiite pilgrims panicked by rumors of a suicide bomber broke into a stampede on a bridge, leaving some 1,000 of them dead. Police later said no explosives were found on the bridge and poor crowd control and the climate of fear in Iraq appeared largely to blame. Sunni insurgents have often targeted such gatherings to foment sectarian war. Brig. Gen. Qassim al-Moussawi, an Iraqi military spokesman for Baghdad, said the government was considering a driving ban but had not made a decision. However, Iraqi security forces will intensify checkpoints and marchers will be banned from carrying weapons, cell phones or even bags, and he urged people to ignore rumors, al-Moussawi said. It was not clear how such measures could be enforced. The United States and Iran, meanwhile, held an expert-level meeting on security issues in Baghdad, more than two weeks after rare talks at which the ambassadors of the two arch-enemies agreed to establish a committee to discuss efforts to stabilize Iraq. Washington has accused Teheran of fueling the violence by arming and training Shiite extremists, but it agreed during the July 24 ambassadorial talks to set up a security subcommittee to carry forward talks on restoring stability in Iraq. The detention of four Iranian-Americans in Iran has deepened tensions between Washington and Tehran, whose relations were already strained over Iran's nuclear program and its support for radical militant groups like Lebanon's Hezbollah and the Palestinian Hamas and by US military maneuvers in the Persian Gulf. Washington has called for their release and says the charges are false. A US Embassy spokesman, Lou Fintor, said Monday's discussions were "frank and serious" and focused on the violence plaguing Iraq. "We agreed to continue our discussions at a date to be established through diplomatic channels," Fintor said. The talks come as the US military steps up accusations that Tehran is arming and training Shiite militants to attack American forces. Lt. Gen. Raymond Odierno, the US second-in-command, said Sunday that rogue Shiite militiamen with Iranian weapons and training launched 73 percent of the attacks that killed or wounded American forces last month in Baghdad, nearly double the figure six months earlier. Tehran has denied US allegations that it is fueling the violence in Iraq. A US soldier was killed and two were wounded Sunday during fighting in eastern Baghdad, the military said Monday. The death announcement provided no more details, but eastern Baghdad is predominantly Shiite and has seen frequent attacks on American forces by Shiite militia fighters. Tal Afar, which was cited by US President George W. Bush last March as a success story after major military operations against insurgents, has been the frequent site of Sunni extremist attacks in the past year. Many of them stemmed from allegations by a 50-year-old Sunni Arab woman, who came forward last February and said Iraqi soldiers raped her when they raided her house searching for weapons. Sunni insurgents have kidnapped and killed dozens of Iraqi security officials in response. The city recorded one of the deadliest days since the start of the Iraq war, when at least 152 people died in truck bombings on March 27. That attack prompted Shiite militants and police to go on a shooting rampage against Sunnis, killing as many as 70 men execution-style. Abdullah, who also is mayor of Tal Afar, said the blast occurred 10 kilometers northeast of the city center. Sixty decomposing bodies also were found in a mainly Sunni area that had been under the control of al-Qaida in Iraq west of Baqouba, according to a Diyala provincial police official. US and Iraqi forces recently have touted successes in an operation aimed at restoring control in the volatile region northeast of Baghdad. The bodies were promptly buried in the Sharif al-Radhi cemetery in Baqouba, the official said. The US military said it had no information about such a discovery. At least 29 people were killed or found dead elsewhere in Iraq, according to police. Those included the bodies of five soldiers who had been ambushed by gunmen as they were on their way home for vacation the night before north of Tikrit and nine civilians killed by a roadside bomb that struck during rush hour in a predominantly Shiite area near Baghdad.