Police blocked highways today, and an official said 15,000 people were detained following the assassination of a former defense minister, the most prominent victim of the nation's 10-year-old guerrilla war. Enrique Lopez Albujar was killed Tuesday when three Shining Path rebels armed with machine guns killed him near a shopping center in a Lima suburb, police said. He died at a military hospital with at least 10 bullet wounds. Witnesses said the four gunmen fled in an automobile. Police units aided by six helicopters searched through Lima and its outskirts Tuesday night and early today, stopping about 8,000 cars in a search for suspects, police said. Most of the 15,000 detained were taken in for not carrying documents and are expected to be released in the next few days, an Interior Ministry spokesman said on condition of anonymity. Lopez was the first person who had served on the Cabinet to be killed in guerrilla violence that has claimed the lives of hundreds of federal and local officials _ more than 130 in 1989 alone. The main guerrilla faction is the Shining Path, a fanatical Maoist-inspired group that has been fighting to topple Peru's elected governments since 1980. Witnesses interviewed by The Associated Press said Lopez had an office in the shopping center and usually arrived at the same time every day, often accompanied by a bodyguard. Speaking to reporters at the government palace, President Alan Garcia said Lopez was entitled to a military guard and that he didn't understand why Lopez was alone when he was attacked. ``It pains me and I regret that he was alone in spite of the situation of war we are living in,'' Garcia said. Lopez was named the country's first defense minister by Garcia, taking office in 1987 when the ministry was formed. Previously, the army, navy and air force had their own ministries. He served until May, when he was replaced by army Gen. Julio Velasquez. Shining Path began its insurgency in Ayacucho, in the Andes mountains 235 from the capital. In the past year, it has stepped up assaults in Lima. Last fall, it tried to disrupt municipal elections by killing local officials across Peru. But Peruvians defied death threats and turned out in large numbers to vote on Nov. 12. Peruvians expect the Shining Path to step up attacks as presidential elections slated for April draw closer. The Shining Path operates throughout the highlands, including in the Huallaga Valley, part of the coca-producing jungle in the northeast and the single largest source of coca-leaf in the world. Authorities say the rebels operate in league with drug-traffickers in the valley, protecting them from police in exchange for a share of drug profits. The government says more than 17,500 people, including government forces, civilians, guerrillas and American reporter Todd Smith of The Tampa Tribune have been killed in the insurgency. Authorities routinely accuse the Shining Path of massacring peasants, but in November Amnesty International accused government forces of becoming equally savage in their effort to crush the insurgency. The London-based human rights group said both sides were guilty of torture, mutilation and murder.