Caracas, Sep 18 (IANS/EFE): Television coverage of a speech by opposition presidential candidate Henrique Capriles was interrupted Monday when incumbent head of state Hugo Chavez commandeered Venezuela's airwaves for an event marking the start of the school year.

Critics have accused the leftist president of abusing the mechanism known as the "cadena obligatoria", under which the government can compel all television and radio stations to preempt regular programming for an official event.

Monday's cadena came as Globovision TV was broadcasting a speech by Capriles to supporters in Caracas.

During the event, Chavez interacted with a group of pupils in the capital neighbourhood of Macarao and made a video hookup with a school in an indigenous community in the northwestern state of Zulia.

Capriles, whose speech continued to be transmitted via the Web by Globovision, expressed his outrage on Twitter.

"We're also going to defeat the abuse of power in the middle of an election campaign expressed in the cadenas (Oct 7)," he tweeted, referring to the Oct 7 election.

On Aug 15, the civic group Public Space launched a campaign to ask that cadenas obligatorias be suspended during the presidential campaign since they harm the principle of equal access to the media for all candidates and/or parties.

Public Space director Carlos Correa told EFE that between July 1, when the campaign officially commenced, and Aug 9 Chavez has used the cadena obligatoria provision for an average of 32 minutes per day.

Capriles is the main challenger to Chavez's bid to remain in office through 2019.

The 58-year-old former army colonel took office in 1999.