A soldier standing trial for the summary execution of four detainees at a police detention center in Yogyakarta's Sleman district in March claims that he shot at the victims in self-defense after one of them attacked him with an iron rod.

Speaking at his court martial in Yogyakarta on Tuesday, Second Sgt. Ucok Tigor Simbolon admitted to storming the Cebongan jail on March 23 with the intent of finding the detainees who had been arrested for the murder of a fellow Army Special Forces (Kopassus) personnel four days earlier.

He said that one of the detainees then struck at him with a rod through the bars of his cell and hit him on the shoulder. He then tried to identify the person who had hit him, but at that point, the culprit had dropped the rod.

"I immediately pulled out my gun as I was afraid they would reach for it. I acted quickly and shot that person," Ucok said, as quoted by Detik.com.

He was testifying as a witness for a co-accused, Second Sgt. Sugeng Sumaryanto, who was also involved in the attack.

Ucok admitted to killing two people who had been locked inside the cell and then pursuing the others inside and also gunning them down. He added that afterward, he was dragged out of the cell by another Kopassus member and fleeing the jail.

Ucok is one of three Kopassus personnel facing a possible death penalty for the jail raid and execution of suspected gang members Hendrik Angel Sahetapi, Yohanes Juan Manbait, Gameliel Yermianto Rohi Riwu and Adrianus Candra Galaja.

Nine other Kopassus personnel are also facing a military tribunal and could receive life sentences for their roles in the incident that shocked the nation.

Following Tuesday's hearing at the Yogyakarta military tribunal, Ucok, Sugeng and fellow defendant Second Cpl. Kodik apologized for "inconveniencing" the Cebongan officials whom they had held at gunpoint while carrying out the execution of the detainees.

The officials, including chief security officer Margo Utomo and wardens Supratikno and Indrawan, all welcomed the gesture from the soldiers.

"On behalf of my friends, officers of the Cebongan jail, I accept the defendants' apology," Margo said. "We were simply doing our jobs, so we do not have anything personal to hold against them," he said after testifying.

None of the Kopassus members has expressed any kind of remorse for gunning down the four unarmed men.