Presidential candidates Nicolas Maduro and Henrique Capriles have begun Venezuela's election race with scathing personal attacks.

Mr Maduro was sworn in as acting president after Hugo Chavez died of cancer last week and he is seen as favourite to win the 14 April vote.

He is bolstered by an oil-financed state apparatus and a wave of public sympathy over Mr Chavez's death.

"I am not Chavez, but I am his son," Mr Maduro told thousands of supporters as he formally presented his candidacy to the election board today.

"I am you, a worker. You and I are Chavez, workers and soldiers of the fatherland," the former bus driver and union activist added.

Mr Chavez made clear before his fourth and last cancer operation in December that he wanted Mr Maduro to be his Socialist Party's candidate to succeed him if he died.

Mr Maduro has vowed to continue the radical policies of Mr Chavez's 14-year rule in the South American OPEC nation, including the popular use of vast oil revenues for social programmes.

But Mr Capriles is promising a tough fight.

"Nicolas, I'm not going to give you a free passage ... you are not Chavez," Mr Capriles said in a combative speech yesterday.

He also accused Mr Maduro of lying to minimise Mr Chavez's medical condition while he prepared his candidacy.

"Nicolas lied to this country for months," Mr Capriles said.

"You are exploiting someone who is no longer here because you have nothing else to offer the country ... I don't play with death, I don't play with suffering, like that."

At stake in the election is not only the future of Mr Chavez's leftist "revolution," but the continuation of Venezuelan oil subsidies and other aid crucial to the economies of left-wing allies around Latin America, from Cuba to Bolivia.

Government officials said Mr Capriles was playing with fire, offending Mr Chavez's family and risking legal action by criticising the handling of his illness and death.

"You can see the disgusting face of the fascist that he is," a visibly furious Mr Maduro said, alleging that the opposition was hoping to stir up violence.