Armed gunmen took 40 bus passengers hostage Tuesday -- killing one of them, according to police -- in a southern region so notorious for mass kidnappings it has been nicknamed Russia's "Bermuda Triangle."The kidnappers boarded the shuttle bus as it left the Rostov-to-Baku highway, spanning Russia's southern fringes, for a stop at Mineralniye Vody. They produced weapons and machine-gunned a passing police patrol car. It was the third such attack on the road in six months. Mineralniye Vody airport police said the three hijackers had killed one hostage. After driving the bus to the town's airport, with the body and the live passengers on board, they opened negotiations with police and Interior Ministry officials. "They're not letting anyone get close," one airport policeman said by telephone. He said the bus was parked about 200 meters from the airport building. A woman hostage had been dispatched with the kidnappers' first messages to Russian authorities, he added, but the two sides were now using walkie-talkies to communicate. Officials were unable to confirm or deny conflicting press reports that either 16 or six hostages had been freed. Russia's Mayak radio station said the trio demanded weapons, a ransom of $5.8 million and a free flight out of town. A Mayak correspondent said the gunmen wanted two helicopters to take them to Makhachkala, capital of the neighboring Dagestan ethnic republic on Russia's border with Azerbaijan. Two earlier multiple kidnappings in the area of Mineralniye Vody -- one in December and one last month -- have followed much the same route.