MEXICO CITY (AP) — A lone gunman has killed the mayor of the small town of Pacula in the central Mexico state of Hidalgo.

More than 60 mayors or mayors-elect have been killed in Mexico since 2006, often by criminal gangs.

The Hidalgo state prosecutors' office said Mayor Alejandro Gonzalez Ramos was travelling in a truck with two town employees when a gunman killed him on Thursday. The two employees were not seriously injured. It said the case is under investigation.

The conservative National Action Party condemned the killing, saying "we urgently need to stop the violence we Mexicans are experiencing."

Two mayors were killed in April alone.

There have been concerns that the violence could affect the country's July 1 elections.