Yogyakarta: A group of well-trained gunmen stormed an Indonesian jail on the main island of Java early on Saturday and executed four detainees accused of murdering a special forces soldier.

At least 17 masked gunmen angry over the killing of a member of Indonesia’s elite military unit, known as Kopassus, allegedly by the four men detained in Yogyakarta’s Cebongan prison, broke into the jail, said local police chief Brig. Gen. Sabar Rahardjo. The attackers tortured several guards and forced them to open the jail cell just after midnight Saturday.

The four detainees were dragged from their cell and shot with automatic weapons before the gunmen destroyed surveillance cameras and fled, he said.

“They looked very professional,” Rahardjo said. “Their acts were completed in just five minutes.”

Rahardjo says two guards were injured during attack.

Police and military investigators were still collecting evidence from the scene, and several witnesses were being questioned.

“Whoever did it should be immediately arrested and prosecuted,” said Djoko Suyanto, coordinating minister for Political, Legal and Security Affairs.

Rahardjo said Saturday’s attack was apparently triggered by the murder of a Kopassus member Tuesday at a Yogyakarta cafe. Four suspects were arrested by police hours later and three others remain at large.

Kopassus troops have been implicated in a range of war crimes and human rights violations over the years. Indonesian officials say they have worked to address the problems.

Earlier this month, dozens of Indonesian soldiers angry over the killing of a comrade by police, attacked and burned down a police headquarters and four other stations in South Sumatra province.