* Interpol offers assistance in probe
* Opposition critic says Morales "playing the victim"
LA PAZ, April 17 (Reuters) - Bolivia launched an investigation on Friday into a suspected militant group that police say was plotting to kill President Evo Morales, but the opposition slammed the probe as an "international show."
Three suspected mercenaries were killed in a shootout on Thursday in the anti-Morales stronghold of Santa Cruz after police moved to arrest a gang that officials say traveled from Ireland or Croatia to kill leading public figures in the Andean nation.
"The investigative work is now in the hands of prosecutors. I hope they do their work quickly so we can have clear and concrete information" about who was behind the conspiracy, police chief Victor Hugo Escobar told state television.
Interpol has offered to help Bolivia with the investigation. But opposition Senate chief Oscar Ortiz said investigators "should aim to find the truth, instead of helping the president stage an international show".
Ortiz attacked Morales for "playing the victim" and said the country's first indigenous leader was trying to disparage the eastern city of Santa Cruz because he lacked support there.
Morales has accused right-wing politicians and business leaders in Santa Cruz of organizing violent protests there last year to try to destabilize his government.
On Thursday, he said the rightist opposition wanted to "riddle us with bullets," referring to himself and the vice president.
Government officials said the suspected conspirators had also targeted Santa Cruz Governor Ruben Costas, a fierce Morales' critic. They said the men were likely behind a dynamite attack on the residence of Roman Catholic Cardinal Julio Terrazas earlier this week. The cardinal was not home at the time.
"The terrorist group had a strategy and part of the strategy was to attack the cardinal ... and (take) other actions, not only against the president or vice president, but other authorities as well," Deputy Interior Minister Marcos Farfan told the Erbol radio network.
Farfan said the suspected plotters tried to blow up a navy boat on which Morales met with Cabinet ministers two weeks ago and aimed to trigger "a spiral of violence" in Bolivia.
The head of the Organization of American States, Jose Miguel Insulza, condemned the suspected assassination plot on Friday after meeting with Bolivia's foreign minister in Trinidad and Tobago, where Morales was attending the Summit of the Americas.
Confusion lingered over the nationalities of the three men killed. State news agency ABI reported that one of them was a Bolivian-Hungarian, Eduardo Rozsa Flores, who fought in separatist movements in the former Yugoslavia.
ABI said the other two men who died in the gunfight hailed from Ireland and Romania, although Bolivian authorities initially said two of the men had been Hungarian.
Police arrested two others in the Santa Cruz raid, whom local media identified as a Bolivian and a Hungarian. Authorities said police confiscated sniper rifles, high-caliber guns and other explosives from a nearby building. (Additional reporting by Carlos Quiroga in La Paz and Damian Wroclavsky in Port of Spain; Editing by Peter Cooney)
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