He was also quick to dismiss criticism from the Hungarian government about whether the men were involved in a plot to kill him.
"I can also condemn these declarations. I will never lie. If the prime minister defends these citizens, well, then I can think it was him who sent them to make an attempt against me, against this democracy."
Morales had earlier said he would co-operate with any international inquiry into the alleged plot and killings.
The men were killed last Thursday in an exchange of fire with police at a hotel in Santa Cruz.
|Police are holding two men: Elod Toaso, left, and Mario Tadic, right [EPA]
Bolivian officials have named the group's leader as Eduardo Rozsa-Flores, a Bolivian who also held Hungarian and Croatian passports, and who fought in the Balkan wars.
Michael Dwyer, an Irish bodyguard, and Arpad Magyarosi, an ethnic Hungarian from Romania, were also killed, the Bolivian authorities have said.
Peter Balazs, the Hungarian foreign minister, said his government had not received enough information from the Bolivian authorities.
"I have doubts, and I don't see evidence that these people, who were killed by a police squad or detained, these people really planned the assassination of the president."
Rozsa-Flores said in an interview given to Hungarian television last year that he was forming a militia in Bolivia to defend Santa Cruz against the central government.
Morales, who accused leaders in Santa Cruz of organising violent protests last year, has linked the suspected plot to right-wing opponents he says are seeking to destabilise his government.
The opposition has denied links to the alleged plot.
Morales has announced several similar plots against him in the past although the results of investigations have not been made public.
The Bolivian president, a socialist, is the country's first indigenous president and has faced determined opposition from wealthy regions of the country, including Santa Cruz, over his plans to redistribute land to the poor.