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

A gunman has shot dead two top aides of the mayor of Mexico City, Clara Brugada. The mayor's private secretary, Ximena Guzmán, and Brugada's adviser, José Muñoz, were killed on their way to work on Tuesday morning local time.

The murders of two aides to Mexico City's Mayor Clara Brugada were carefully planned by experienced gunmen, prosecutors said.