Gunmen killed Praxedis Guerrero's mayor Rito Grado and his son in Ciudad Juarez, north of Mexico, the prosecutor's office of Chihuahua state said on Sunday.

The office said in a statement that both victims were killed on Saturday night in their house of Ciudad Juarez.

The incident occurred at about 9:30 p.m. Saturday (0230 GMT, Sunday).

The authorities said the victims were shot by AK-47 bullets, adding they found at least 60 bullet shells at the scene.

They believed it was a revenge case conducted by organized crime gangs.

The state of Chihuahua has the country's highest rate of violence and crime.

Media reports said that at least 7,100 deaths related to organized crimes were reported in Mexico in 2010.