(Adds details from scene) By Dean Yates BAGHDAD, April 12 (Reuters) - A large truck bomb killed up to eight people on a bridge in northern Baghdad on Thursday, cutting the steel structure in half and sending several cars plunging into the River Tigris below, Iraqi police said. The blast occurred just before the morning rush hour, sending a cloud of smoke into the air and rattling windows in neighbouring areas. A large chunk from the middle of the Sarafiya bridge had collapsed into the river. Another section at one end was also damaged, suggesting there were two bombs. U.S. and Iraqi forces launched a security crackdown in the capital two months ago that has managed to reduce death squad killings, but car and truck bombs remain a problem. Police put the death toll at between five and eight from the bombing. They said up to 22 people were wounded. Police patrol boats and divers searched the muddy waters for survivors. Four or five cars had fallen into the river, police said. Some Iraqi security officials on the scene said the truck had been parked in the middle of the bridge before it exploded. One police official said security forces had been suspicious about the truck and tried to block off roads leading to one of Baghdad's oldest bridges before the explosion. "We were sleeping when suddenly we heard a huge explosion. We came out and saw the bridge had fallen," said Saad al-Khazali, a local resident who rushed to the scene. Hours after the blast, officials surveyed the damage. The River Tigris cuts Baghdad in half and the Sarafiya bridge is a key artery in the northern part of the city. Two of the dozen bridges that cross the Tigris in Baghdad have been shut for security reason, and the loss of the Sarafiya link will worsen traffic jams that have already been aggravated by scores of checkpoints set up under the security plan. The Sarafiya bridge is often used by minibuses and commercial vehicles travelling from central Baghdad to markets in the city's north. The Baghdad security operation is seen as a final attempt to halt Iraq's slide into civil war between majority Shi'ites and minority Sunni Arabs who were dominant under Saddam Hussein. U.S. President George W. Bush is sending 30,000 more troops to Iraq, mainly to help with the Baghdad offensive. Around 100,000 American and Iraqi forces are already in the capital for the push and all reinforcements should arrive by the end of May or early June. The U.S. military said on Wednesday that for the third month in a row, civilian casualties had declined in Baghdad but that in the same period there had been an increase in casualties across Iraq as militants step up their attacks outside the city. The U.S. military also accused Iranian intelligence services of providing weapons to militants in Iraq and said gunmen were being trained in Iran in the use of lethal roadside bombs. The United States accuses Tehran of trying to destabilise Iraq. Iran denies the accusations. Washington has hardened its rhetoric over Shi'ite Iran's alleged role in the war in Iraq and tension has been growing between the two arch-foes over Tehran's nuclear ambitions. (Additional reporting by Aseel Kami and Yara Bayoumy)
