The entire police force in the Mexican town of Ocampo were disarmed and arrested for allegedly obstructing an investigation into the murder of the mayor ahead of country-wide elections on Sunday.

Fernando Angeles Juárez was killed on Thursday morning after three gunmen broke into the ranch where he lives just as he was preparing to start a day's campaigning, local media reported.

Over 120 politicians have been killed across Mexico since September, when campaigning began ahead of the country’s July 1 general elections. Voters are being ask to elect over 3,000 local officials, as well as a new president and a new legislature.

Mr Angeles Juárez was the third politician killed in the state of Michoacán in a week.

After his murder, Michoacán state forces went to Ocampo on Saturday with a warrant to arrest the town’s public security secretary Oscar González for questioning, but were forced to retreat when local police officers under his control fired shots into the air.