The former mayor of a town in western Mexico, who had survived two earlier assassination attempts, has been beaten to death.
The body of Maria Santos Gorrostieta, 36, was found in a ditch with a blow to the head three days after her family had reported her missing.
When she was mayor of the town of Tiquicheo she was twice shot at by gunmen, who also killed her husband.
Mexican officials have increasingly become targets of drug cartels.
There have been calls for the federal government to do more to step up their security.
Ms Gorrostieta was the mayor of Tiquicheo, in western Michoacan state, from 2008 until 2011.
Unidentified gunmen ambushed her in October 2009 as she was travelling in a car with her husband Jose Sanchez.
Mr Sanchez died of gunshot wounds sustained during the attack.
Three months later Ms Gorrostieta was seriously injured in a second ambush.
After being released from hospital following the second attack on her life, she said she did not know why she was being targeted.
"I have a clear conscience, I have never had any issues of any kind, be it money, family or crime related, and I have never had any fights with any neighbours or residents of my town, or any other town," she said.
She also published pictures of the scars she had sustained in the two attacks in her local newspaper with a message thanking her family and supporters and vowing to "continue fighting, true to my ideals and my convictions, convinced that the truth will make us free".
About two dozen mayors have been murdered since President Felipe Calderon declared war on drug traffickers six years ago.
While police say the motives behind the killings are not always clear, most attacks on local officials have happened in small and medium-sized towns in regions disputed by rival drug gangs.