Six men accused of being involved in the assassination of Ecuador’s anti-corruption presidential candidate Fernando Villavicencio in August were assassinated in prison on Friday, according to the prisons department, just a week before a key run-off election.

The killings took occurred in a penitentiary in Guayaquil, the South American country’s largest city, according to the attorney general’s office.

Ecuador’s government swiftly condemned the killings.

Outgoing President Guillermo Lasso pledged “neither complicity nor cover-up” in getting to the bottom of the killings, in a post on social media platform X, formerly known as Twitter.

“Here the truth will be known,” he said.

The SNAI prisons agency said in a statement the six men were all Colombian nationals. It gave no more details of the killings.

The government has said authorities are determined to identify those behind Villavicencio’s murder.

Villavicencio, a prominent journalist, was gunned down less than two weeks before a first round general election as he left a campaign event in the capital, Quito.

Police arrested the six Colombians on the day of Villavicencio’s assassination. A seventh suspect, also Colombian, was shot and killed by police, while other suspects were later arrested.

The second round run-off vote is scheduled for Oct. 15, the culmination of an election cycle marred by numerous incidents of violence.

Business heir Daniel Noboa, who holds a narrow lead in some polls ahead of the run-off, said in a social media post that the government must provide details of what occurred at the prison and that peace must be restored in the country.

His main rival for the presidency is Luisa Gonzalez, a protege of leftist former President Rafael Correa. She has said that surging crime is unprecedented and that voters should not allow “terror” to stop them from voting for change.