(Adds reaction from Croatia, Del Ponte's spokeswoman)
THE HAGUE, Sept 27 (Reuters) - The U.N. war crimes tribunal sentenced former Yugoslav army officer Mile Mrksic to 20 years in prison on Thursday for effectively enabling the massacre of 194 people in the Croatian town of Vukovar in 1991.
Judges sentenced a second ex-officer, Veselin Sljivancanin, to five years for torture but cleared him of the most serious charges, while a third ex-officer, Miroslav Radic, was acquitted of all 8 counts of war crimes and crimes against humanity.
The court's rulings caused shock and anger in Croatia, where Vukovar is viewed as one of the most brutal episodes of the Balkans wars.
"I don't want to comment on the verdicts because they are so shameful," Croatian Prime Minister Ivo Sanader told state news agency Hina. "
Prosecutors had tried to prove the three men were responsible for the killing of at least 264 people who had sought shelter in Vukovar's hospital early in the 1991-95 war, and had sought life sentences for all three.
After Vukovar fell to Yugoslav forces after a three-month siege, people sheltering in the hospital hoped to be evacuated in the presence of international observers.
Instead several hundred were selected by Serb forces, then taken to a farm where they were brutally beaten and shot dead, their bodies dumped into a mass grave.
Prosecutors said this group were largely civilians, but the judges ruled members of the Croatian forces were also hiding in the hospital, pretending to be patients or hospital staff.
They further ruled that those selected were seized because they were suspected Croatian fighters, therefore giving them prisoner of war status, and as such invalidating all charges of crimes against humanity against the three accused, which apply only to offences against civilians.
Judges added that the three were not criminally responsible, as the killings themselves were not committed by troops under their command, although Mrksic, 60, had in effect allowed the killings to happen because he left the detainees in the hands of local Serb paramilitaries, who he knew would seek revenge.
In failing to order more military police to supervise the detainees and protect them from the paramilitaries Sljivancanin had enabled their torture, Judge Kevin Parker said.
Sljivancanin was in charge of evacuating the hospital and separating out suspected Croatian fighters, although it was first planned to take them to a Serbian prisoner of war camp.
The court therefore threw out the prosecutors' argument that the three accused had intended to murder the Croats all along.
"There is no direct evidence which establishes this," said Judge Parker.
A spokeswoman for the U.N.'s chief war crimes prosecutor Carla del Ponte said: "The prosecutor finds it incomprehensible that someone who is convicted for the torture of 200 people can receive only a sentence of five years."
Croatian Prime Minister Sanader said the ruling represented "a defeat of the whole idea of the Hague tribunal."
"The whole world witnessed the suffering of civilians in Vukovar. The victims did not deserve such verdicts," he said.
Binazija Kolesar, a nurse in the hospital at the time said she was shocked at the lax sentences, especially in the case of Sljivancanin.
"He is responsible for the fact that the wounded were taken from the hospital," she told Reuters in Vukovar. "We all saw him in the hospital and we know that he was the one who was making decisions. I have no words. No sentence would be too high." (Additional reporting by Zagreb bureau)
Our Standards: The Thomson Reuters Trust Principles.