UPDATE 2-Venezuela begins shutdown of 34 radio stations

* Chavez says stations no longer belong to 'bourgeoisie'

* Calls closures part of effort to democratize airwaves

* Critics say the move attacks freedom of speech (Adds Chavez comment)

By Raymond Colitt and Ana Isabel Martinez

CARACAS, Aug 1 (Reuters) - More than a dozen of 34 radio stations ordered shut by the Venezuelan government went off the air on Saturday, part of President Hugo Chavez's drive to extend his socialist revolution to the media.

The association of radio broadcasters said 13 stations had stopped transmitting, following an announcement Friday night by government broadcasting watchdog Conatel that 34 radio outlets would be closed because they failed to comply with regulations.

Critics said the crackdown infringed on freedom of speech and that owners were not given the right to a proper defense.

"They're closing the space for dissidents in Venezuela," William Echeverria, head of the National Council of Journalists, told RCTV, a private cable TV station, which did not have its broadcasting license renewed in 2007.

Chavez defended the closures, calling them part of the government's effort to democratize the airwaves.

"We haven't closed any radio stations, we've applied the law," Chavez said on state television. "We've recovered a bunch of stations that were outside the law, that now belong to the people and not the bourgeoisie."

Chavez supporters say they are waging a "media war" against private news companies and have denounced in recent days what they say is a renewed offensive by privately owned domestic and international media to discredit Venezuela.

Diosdado Cabello, the public works minister who also oversees Conatel, said some of the radio stations were shut because they did not have their broadcasting licenses renewed and others transferred them illegally to new owners.

Conatel delivered an order to CNB radio in Caracas before dawn for its five stations to stop transmitting by 8 a.m., the station said on its website.

At CNB's headquarters in downtown Caracas, hundreds of CNB employees and government critics gathered to protest the shutdown. Some later marched to Conatel.

CNB said it would continue to broadcast on its Internet site, www.cnb.com.ve.

'MUTILATOR OF RIGHTS'