CULIACAN, MEXICO (AFP) - The son of drug lord Joaquin "El Chapo" Guzman has been released following his abduction earlier this week from a Mexico bar, a member of the Sinaloa cartel leader's family said.

Mr Jesus Alfredo Guzman Salazar, 29, was freed along with the five other men with whom he was kidnapped, a relative who requested anonymity for security reasons told AFP.

"They were negotiating all this time, but now are free and well," the source said, adding that some of the captured men were already back in Sinaloa state.

Mr Guzman Salazar - one of Guzman's sons from his first marriage - was attending a celebration early on Monday at a restaurant and bar in the resort city of Puerto Vallarta when gunmen in pick-up trucks swooped in and kidnapped five of his six companions.

The younger Guzman - himself a key operator in the Sinaloa cartel who is wanted for arrest under a 2009 warrant - was identified by the Jalisco state prosecutor's office based on security camera footage.

Notified by AFP about the reported release, the Mexico Attorney-General's office said simply that it is "still working on the investigation".

The authorities had said they suspected the gunmen who seized the men were from the Jalisco New Generation cartel, an upstart rival of the Sinaloa cartel.

The governors of western Jalisco and Sinaloa states, where the rival gangs are based, have warned of possible reprisals.

The elder Guzman is the jailed boss of the powerful Sinaloa cartel and one of the most notorious drug lords in the world.

He is now in a maximum-security federal prison in the northern city of Ciudad Juarez and fighting extradition to the United States.