Two of four kidnapped journalists, who were abducted by alleged drug gangs earlier in the week in Mexico, have been rescued.

Alejandro Hernandez, a cameraman for Mexico's biggest televesion network, Televisa, and Javier Canales, another cameraman for Multimedios Television, were freed on Saturday in a police raid in the northern city of Gomez Palacio.

Another kidnapped journalist, Hector Gordoa, had already been freed on Thursday.

All of the journalists had been covering a prison scandal in the northern state of Durango, reporting on gunmen who had been permitted to leave the prison to allegedly commit murder.

Drug gangs have been busy in their eagerness to silence journalists who have reported on drug-cartels and their activities.

Since 2006, at least 30 journalists have been killed in Mexico.