Asuncion - Suspected Brazilian gangsters blasted into a secure vault in southeastern Paraguay on Monday and robbed millions of dollars, leaving a policeman dead in what officials called the "robbery of the century."Around 50 gunmen with explosives and heavy arms left the city of Ciudad del Este looking like a warzone after a two-hour overnight assault on a security firm and police headquarters, authorities and witnesses said.Officials said it was an unprecedented attack even for Ciudad del Este, a key trading hub near the borders of Brazil and Argentina in an area linked to drug gangs.The robbers set vehicles on fire to block roads and detonated explosives near the city's police headquarters as a diversion.They blasted their way into the premises of Prosegur, a firm that specialises in securely transporting cash."The noise rang out around the city like bombs in a war," one man who witnessed the attack, Antonio del Puerto, told AFP.Television images from the scene showed the Prosegur building was virtually destroyed, with missile casings lying around and burned-out vehicles in the streets.Police reports said the attackers included members of the Sao Paulo-based First Capital Command, one of Brazil's most powerful drug gangs.Anti-aircraft gunPublic prosecutor Denise Duarte said the men wore masks and spoke Portuguese.She said the Prosegur vault "was full" at the time of the robbery. Police said the vault can hold up to $40 m dollars in cash but authorities had yet to the confirm the amount stolen.The attackers left behind several abandoned vehicles including armoured trucks, one of them with an anti-aircraft gun mounted on it."The security firm's premises has been destroyed and the attack caused chaos and terror in the city," the governor of the surrounding Alto Parana state, Justo Zacarias, told reporters."Nothing like this has ever happened in Paraguay."Paraguay's police chief Luis Rojas said he had contacted the forces in Brazil and Argentina to help catch the robbers."I am going to seek the resources and the best men to work to catch these people," he said.