ACAPULCO, Rioting inmates at a Mexican prison beheaded and mutilated their rivals Thursday, leaving 28 dead and three wounded, officials said.

Bodies were found strewn around the maximum-security wing, the kitchen, a prison yard and a conjugal visits area after the pre-dawn riot at the CERESO federal prison in Acapulco, said the security spokesman for the state of Guerrero, Roberto Alvarez.

"The incident was triggered by a permanent feud between rival groups within the prison," he told a press conference.

State police have regained control of the prison, backed by federal police and the army, which set up a security cordon outside, he said.

The governor has ordered an investigation, including of prison staff, he said.

Officials initially gave a death toll of five. Alvarez had earlier said that victims were stabbed and beaten to death.

Guards said some of the victims had their throats slit, according to an internal state police report.

Mexico's chronically overcrowded prisons are frequently hit by riots and jailbreaks.

Acapulco, a resort town on Mexico's Pacific coast, has been hit by grisly violence between warring drug cartels in recent years.

It is just one of the hotspots in Mexico's war on drugs.

The country has seen a wave of bloodshed in the past decade that has left more than 200,000 people dead or missing as drug cartels wage war on each other and Mexican security forces.

-AFP