MEXICO CITY (Reuters) - A former mayor and his son were killed on Wednesday in central Mexico, adding to an uptick in murders of politicians ahead of national elections later this year.

Miguel Angel Licona, 76, a former mayor of the municipality of Mixquiahuala in the state of Hidalgo, was shot dead along with his son, according to a statement from state prosecutors.

Licona had been mayor for President Enrique Pena Nieto’s Institutional Revolutionary Party (PRI) in the 1990s.

The state attorney general’s office said that investigators had ruled out a political motive to the murder.

In October, another former mayor in Hidalgo was murdered but the government also ruled out any tie to politics and said the killing was the result of an armed robbery.

In recent months, about a dozen politicians, officials and candidates for elected office have been killed in states where there are struggles between criminal groups for the control of drug trafficking routes.

Mexico last year registered its highest murder total since modern records began, according to official data, dealing a blow Pena Nieto’s pledge to get gang violence under control ahead of elections this year.

On July 1, Mexico will elect its next president as well as more than 600 lawmakers, while many states will also hold local elections. Concerns about rising violence and corruption have hammered Pena Nieto’s popularity.

Violence has in the past flared up during elections in areas of the country where gangs seek to influence local politics.