MORELIA (AFP) - Authorities have found the bruised body of a former regional leader of Mexico's leading conservative party on a street behind a town hall in the violence-plagued state of Michoacan.

Octavio Contreras, the former regional secretary of the National Action Party (PAN), was found late Wednesday with bruises and marks around his neck in the town of Apatzingan, a spokesman for the state prosecutor's office said.

Former president Felipe Calderon, a PAN member, called on federal and state authorities to find the assassins.

He wrote on Twitter that Contreras had been "threatened in the town hall in order to stop publishing what was happening in Apatzingan in social networks", but the former leader did not elaborate.

In one of his last messages on social media, Contreras asked for confirmation of reports that "bad guys" were blocking a road in Apatzingan.

Drug cartels regularly block roads to facilitate drug shipments.

Michoacan Governor Jesus Reyna said on Wednesday that authorities were not ruling out any theory behind the killing.

The federal government deployed thousands of troops to Michoacan in May to stop a wave of killings and extorsion by the Knights Templar drug cartel. The violence prompted several towns to form vigilante groups.

But the violence has continued unabated, even claiming the lives of a vice admiral and his assistant in July by suspected cartel members.

Calderon had himself deployed soldiers to his home state after taking office in December 2006, launching a militarised crackdown on drug trafficking which was followed by a surge in murders.