Mexican authorities have not said whether they see the slayings as targeted. They come after a year of heightened political violence.

The private secretary and an adviser to the mayor of Mexico City were gunned down in an attack in the Mexican capital Tuesday.

Two top aides of Mexico City Mayor Clara Brugada were shot dead after being ambushed by gunmen on a motorbike in a daytime attack in the city center on Tuesday. The victims were the mayor's private secretary,