Authorities have begun handing out police uniforms and assault rifles to vigilantes in western Mexico, legalising a movement formed to combat a vicious drug cartel.

Scores of farmers lined up on Saturday at a cattle farm to receive the blue uniforms of the newly created rural state police force in Tepalcatepec, a founding town of the self-defence militias in the lush agricultural state of Michoacan.

The units were also making their debut in the neighbouring town of Buenavista, which revolted in February 2013 against the cult-like Knights Templars gang because local police failed to protect them.

“With this, we become legal,” said white-bearded vigilante leader Estanislao Beltran, nicknamed “Papa Smurf,” after slipping into his outfit.

“We are part of the government.”

Some 100 new rural police officers then sang the national anthem at a formal swearing-in ceremony in the town square.

“From now on, you are in charge of defending your brothers, your families, your neighbours and anybody who can be harmed by organised crime,” said Alfredo Castillo, the special federal security envoy to Michoacan.

The federal government, which had previously just tolerated the vigilantes, has warned that anybody found carrying weapons illegally after Saturday’s deadline to join the force will be arrested.

After the authorities took down three of the four main Knights Templar leaders, the vigilantes signed an agreement last month to register their guns and put them away at home, or join the rural force.

Vigilante leaders said they still had to hash out details like salaries and who would be in command, though they will work alongside the regular state police.

The militia has faced divisions among its leadership, but more than 3300 out of an estimated 20,000 vigilantes have signed up to join the police force, officials say.

Despite the deadline, Castillo said the vigilantes could be granted a few more days to be deputised in other towns because of an unexpected high demand.