Four imprisoned Guatemalan policemen were killed in their cells Sunday, days after being arrested in connection with the deaths of three Salvadoran politicians, police said.

Rioting inmates also took the warden and other prison officials hostage.

National police spokesman Maria Jose Fernandez said she didn't know who had shot the prisoners.

"It's confirmed, they killed the four of them," Fernandez said. Officers outside the jail in Cuilapa, 64 kilometres east of Guatemala City, showed reporters cellphone photos of the bullet-ridden bodies.

Police said members of the violent Mara Salvatrucha gang rioted in the prison, capturing five prison officials. It was unclear if the riot started before or after the killings. The hostages were still being held late Sunday as about 50 riot police entered the prison.

The four police officers killed included Luis Arturo Herrera, head of the Guatemalan National Police organized crime unit, and three of his officers. They were arrested on Thursday and taken to the prison, occupied mostly by Salvatrucha members, after their lawyer said their lives were in danger at another detention centre in Guatemala City.

On Feb. 19, assailants abducted and killed Eduardo D'Aubuisson — son of El Salvador's late right-wing leader Roberto D'Aubuisson — two other Salvadoran officials and their driver in or near Guatemala City. Their charred bodies were later found along a road about 32 kilometres southeast of city.

Investigators have said they don't know the motive for the murders, but some officials said they suspect the slayings were politically motivated or were linked to the region's powerful gangs and crime groups.

The three slain Salvadoran politicians represented their country at the Central American Parliament, which is based in Guatemala City and has 132 members representing five of the seven Central American nations. They also were members of El Salvador's ruling party, ARENA.

D'Aubuisson's late father was embroiled in scandals as the alleged founder of El Salvador's death squads during its civil war from 1980-1992. The death squads were responsible for the kidnap, torture, and murder of tens of thousands of civilians.