Villavicencio's Build party, or Construye in Spanish, announced on social media it had tapped Andrea Gonzalez to replace the slain 59-year-old in the Aug. 20 vote.

Later on Saturday, the deceased candidate's widow criticized the party's replacement as unlawful.

Villavicencio, an ex-lawmaker and journalist with a track record of exposing corruption, was gunned down last week after leaving a campaign event in the capital Quito despite his own government-provided security detail.

Six suspects - all Colombian nationals whom police accuse of links to criminal groups - have been charged with the murder and remain in custody after a judge on Thursday ordered they remain behind bars as the criminal investigation continues.

Veronica Sarauz, Villavicencio's widow, told reporters on Saturday she holds the state directly responsible for her husband's murder.

"The government still has to provide a lot of answers for everything that happened," she said, after arriving at the press conference with an armed police escort and wearing a bullet-proof vest and helmet.

Sarauz described the party decision to tap Gonzalez as "arbitrary" and said it breaks a law that forbids the vice presidential candidate from stepping down.

The national electoral council must still approve the party's stand-in candidates.

Gonzalez, an environmental activist who has not previously held public office, was selected by Villavicencio to be his running made in the snap election called by outgoing President Guillermo Lasso.

While ballots have already been printed, by law votes for Villvicencio will automatically transfer to the party candidate.

The South American nation of some 18 million has seen a rising tide of violence in recent years, including a sharp increase in the murder rate.

Villavicencio had been polling around the middle of the pack in a field of eight candidates prior to his assassination.

Beyond security, employment and migration have emerged as major campaign issues.