Notorious Mexican drug kingpin Rafael Caro Quintero, convicted of ordering the torture and murder of a US anti-drugs agent in 1985, was freed from prison on Friday in a move that angered the US government.

Caro Quintero had served 28 years of a 40-year sentence for the brutal death of Drug Enforcement Administration agent Enrique Camarena and was released after a Mexican court ruled hes hould have been tried at a state level rather than on federal charges.

The DEA said it was "deeply troubled" by his early release and that it would push for him to be tried in a US court.

"We are reminded every day of the ultimate sacrifice paid by Special Agent Camarena and DEA will vigorously continue its efforts to ensure Caro Quintero faces charges in the United States for the crimes he committed," it said in a statement.

Caro Quintero, who is believed to be 60, holds a special place in Mexican drug lore.

He was one of the leaders of the Guadalajara cartel, a forerunner of the Sinaloa cartel which is currently led by Joaquin "Shorty" Guzman, the country's most-wanted drug lord.

Caro Quintero was freed from the Puente Grande prison in the western Mexican state of Jalisco on Friday morning, according to the state attorney general's office.

"There are various factors, and among them the fact that he already served his time for drug trafficking," a court official said in explaining the release.

Camarena was kidnapped, tortured and murdered in retaliation for his involvement in a number of successful drug busts.

At the time, the United States was furious at a perceived lackluster effort to catch Camarena's killer and the episode marked a low point in US-Mexico relations. Caro Quintero was caught in Costa Rica in 1985.

In June, the US Treasury Department imposed sanctions on18 people linked to Caro Quintero, including six family members, freezing their US assets.