The mass killing was part of an early wave of ethnic cleansing in the 1992-95 Bosnian war, as rebel Bosnian Serb forces clashed with Bosnian Croats and Muslims during the break-up of the multi-ethnic former Yugoslavia.
Darko Mrdja, a 36-year-old former metal worker, confessed at a special hearing at the UN court to taking part in the shootings by a special Bosnian Serb police unit of at least 228 prisoners on Mount Vlasic in central Bosnia in August 1992.
The victims were mostly Muslim inmates of the Trnopolje prison camp, one of the most notorious camps of the war. Along with some inhabitants of the town of Tukovi, they were packed into two buses and taken to a wooded mountainside.
The prisoners had been told they would be exchanged for Serbs detainees and were taken to Travnik, 40 miles north-west of Sarajevo. There they were ordered to kneel close to a deep ravine and the shooting began. A dozen men survived by tumbling or jumping down the cliff.
As commander of a special police unit, Mrdja planned the massacre and shot at the rows of kneeling men, his indictment said.
"Here is where we do the exchange, the living for the living, and the dead ..." it quotes him as having said before opening fire.
Prosecutors and the defence recommended a 15-20 year prison sentence to judges after a plea deal. Mrdja is expected to be sentenced later this year.
Mrdja - a dark-haired man with a goatee beard and glasses - pleaded not guilty 13 months ago to three counts of crimes against humanity and war crimes but changed his plea to guilty on two counts - murder and attempted murder - under the deal.
The third charge of extermination, a crime against humanity, was dropped.
The presiding judge, Alphonsus Orie, told Mrdja: "You along with others participated in the unloading, escorting, and shooting of unarmed men."
When the judge asked him if he understood what he was confessing, Mrdja replied: "Everything is clear to me. I'm guilty." The judge then convicted Mrdja and ordered that a date be set for sentencing.
The former police commander is the latest in a spate of war crimes suspects to plead guilty at the international criminal tribunal for the former Yugoslavia, the most notable of whom is the former Bosnian Serb president Biljana Plavsic, who was sentenced to 11 years for torture.
"I'm guilty of counts two and three," Mrdja told the tribunal. Mrdja was seized by Nato-led troops last June under a sealed or secret indictment - used by the tribunal to prevent suspects knowing they are wanted by the court and going into hiding.