Venezuela's opposition leader Henrique Capriles dismissed as irresponsible on Tuesday a government warning of an assassination plot against him that has further stirred up an already volatile election campaign.

President Hugo Chavez made the surprise claim on Monday evening, implying that elements within the opposition were behind a plan to kill Capriles, the 39-year-old Miranda state governor who is challenging him in an October 7 election.

The declaration of the Socialist Party candidate borders on the irresponsible, like his government is with the insecurity our people have to live with, Capriles said via Twitter.

The latest development adds to a nervous and polarized atmosphere in the South American OPEC member, which the socialist Chavez has dominated for 13 years.

Shots were fired during one Capriles campaign stop in Caracas earlier this month, and officials from Chavez down have pilloried him as a pig, bourgeois and a little Yankee.

Foes frequently call Chavez a dictator.

The president is recovering from cancer surgery and is due to start radiation therapy in the coming days. The treatment is expected to weaken him during the campaign and has triggered rumours in some circles that he has a life-threatening condition.

DISTRACTION?

Nevertheless, Chavez has a healthy poll lead over his rival, thanks, analysts say, to his strong emotional connection with the poor and oil-financed spending on welfare projects.

Capriles, a centre-left politician who hails Brazil as his model, said the assassination talk was a distraction from daily problems troubling Venezuelans, such as a violent crime rate that is among the worst in the world.

Our people have for years been living with insecurity, violence, lack of peace, Capriles said in another tweet. My fight is for a country without violence and we will achieve it!

The governor, who is the candidate of the Democratic Unity coalition that groups the country's main opposition parties, dismissed an offer from Chavez of state protection.

A president should not 'offer' protection to one Venezuelan - he should guarantee it for all, Capriles said.

Chavez gave few details of the alleged plot in a phone call to state television but said Venezuela's head of intelligence met with Capriles aides because there's some information out there that they want to kill him.

Chavez said the plot was not within government supporters, but rather among criminal destabilisers linked to the opposition itself.

Capriles' combative response marked a change in tone. He had sought to avoid confrontation with the Chavez and to project himself as the man to solve grassroots problems, rather than engage in rhetorical battles.

This month, he began a nationwide house-by-house tour in a simple bus and with notably little security.

Wearing T-shirts and often splattered with mud, Capriles has plunged in-and-out of homes and shops, and walked the streets for hours to talk to voters and hear their problems.

Chavez supporters say Capriles has copied the style of their man, who ran a remarkable on-the-street campaign in 1998 to sweep to a first presidential victory and embark on the revolution that has made him one of the world's most recognizable figures.

(Editing by Daniel Wallis and Bill Trott)