The authorities in Guatemala have ordered the arrest of 18 former senior officials and policemen over the killing of seven prisoners in 2006.
The wanted men include the opposition leader Alejandro Giammattei, who was head of the prison service at the time.
He has taken refuge in the Honduran embassy, and says he is the victim of political persecution.
Six other suspects, including three police officers, have been arrested.
They are accused of involvement in the extra-judicial executions of prisoners when the security forces stormed the El Pavon prison outside Guatemala City in 2006 to take back control from criminal gangs.
Other charges related to the killing of three prisoners after they escaped from another jail in 2005.
In both cases, police said the prisoners were shot after confronting officers with fire arms.
The arrest orders followed an investigation by the UN-backed international commission against impunity in Guatemala (CICIG).
The accused "formed part of a criminal organisation based in the interior ministry (ministerio de gobernacion) and civil police that was dedicated to extrajudicial executions of people detained in prisons," CICIG said in a statement.
The group was also involved in other crimes including "murder, drug trafficking, money-laundering, kidnapping, extortion and the theft of drugs", it further alleged.
Among the accused are the former interior minister Carlos Vielman and the former head of the civil police, Erwin Sperisen, both of whom are thought to have fled the country.
The former prison service director Alejandro Giammattei was a losing candidate in the 2007 election that brought president Alvaro Colom to power.
He denies the charges, and has taken refuge in the Honduran embassy saying he fears for his life.
It is not clear if Honduras will grant him political asylum.
Corruption, violence and organised crime are rife in Guatemala. The country also has a long history of impunity, with few cases either coming to trial or resulting in convictions.
The international commission against impunity in Guatemala was set up by the UN in 2006 to help Guatemala reform its justice system and confront organised criminal gangs that have infiltrated the state.
These charges are the first major case CICIG has launched under its new head, former Costa Rican Attorney General, Francisco Dall'Anese Ruiz, who took over in June.
His predecessor, the Spanish prosecutor Carlos Castresana, resigned saying the Guatemalan government had not kept its promises to reform the justice system.