(RTTNews) - The entire police force of a small town in northern Mexico resigned after gunmen attacked their recently-opened headquarters with grenades and assault rifles, local news agencies reported quoting the town's Mayor on Wednesday.

Santos Salinas, Mayor of Los Ramones municipality in the state of Nuevo Leon, confirmed that all of the town's 14-member police force resigned after Monday's attack, which left the newly-opened headquarters damaged and six patrol cars riddled with bullets and shrapnel.

Local media reports quoted Salinas as saying that nobody was injured in the attack, during which the gunmen fired more than 1,000 rounds and hurled at least six grenades into the building. Only three grenades exploded.

He said the Nuevo Leon highway police would now take over the security responsibilities of Los Ramones, a municipality of some 6,000 people.

Nuevo Leon, like many other Mexican states along the border with the U.S., had witnessed a high level of drug-related violence in recent months as rival drug cartels fight each other for control of smuggling routes.

The Mexican government says more than 28,000 of its citizens have been killed in drug-related violence since President Felipe Calderon declared a war on the country's drug cartels late 2006 and deployed thousands of troops to check drug-related violence.

In addition to the fight against drug cartels, Calderon had launched a massive anti-corruption drive named 'Operation Clean-up' to identify and punish public servants with alleged links to the drug cartels.