QUITO—Ecuador’s President Guillermo Lasso on Monday announced a plan to pacify prisons including with involvement of the military, as part of steps to tackle a wave of violence which has left scores of prisoners dead. Fighting between criminal groups in the Penitenciaria del Litoral prison over the weekend killed up to 68 prisoners and injured 25, according to the government. At the end of September 119 inmates were killed at the prison in the city of Guayaquil during the worst incident of prison violence in the country’s recent history. Authorities attribute the unrest to competing drug-trafficking gangs fighting over trafficking routes. Steps to pacify the prisons were agreed with a wide range of officials, Lasso said, describing the violence as one of the biggest crises the country has faced in decades. Ecuador faces “a serious external threat from attack of drug-trafficking mafias, the same ones that intend to take control …