Four explosions aimed at police vehicles and transportation links, including one that derailed a cargo train, wounded eight people Saturday in the volatile Caspian Sea region of Dagestan, officials said. The blasts were the latest in a series of attacks in Dagestan, which suffers from violence spilling over from neighboring Chechnya. Disputes among local ethnic groups and homegrown criminal clans also have plagued the region. A bomb placed on a railway track derailed a cargo train near the border with Chechnya Saturday morning, wounding the train's driver and his assistant, said police spokesman Akhmed Magomayev. The explosion halted railway traffic, delaying four long-distance passenger trains.In Dagestan's provincial capital, Makhachkala, an explosive device went off shortly after midnight as a police vehicle drove by, wounding two officers. When another police vehicle arrived on the scene, another explosion occurred, wounding four senior police officers, according to the regional branch of Russia's Interior Ministry. Several hours later, another explosion occurred in Khasavyurt, a town six miles east of the border with Chechnya. Nobody was hurt, said Andzhela Martirosova, a spokeswoman for the Interior Ministry.