Caracas (AFP) - Venezuelan officials on Wednesday opened an investigation into alleged "irregularities" during an opposition primary, which was won last weekend by a candidate banned from holding office by President Nicolas Maduro's government.

Tarek William Saab, Maduro's attorney general, described the primary as "obviously a fraud" and told journalists in Caracas he had tasked two prosecutors with the probe.

The wide-ranging charges include usurping the functions of Venezuela's National Electoral Council (CNE), criminal conspiracy, making up fictitious voters, and money laundering.

The CNE did not oversee the Sunday vote, which was instead managed by the opposition's own National Primary Commission (CNP).

The CNP said earlier Wednesday that 2.4 million voters took part in the primary that nominated Maria Corina Machado, 56, as the opposition candidate to challenge Maduro in 2024 elections.

The only problem is that Machado has been banned by Venezuelan authorities from holding office for 15 years, effectively ruling her out of the race.

She stands accused of supporting international sanctions against Venezuela. 

'Outside the law'

The United States, which eased some oil and gas sanctions on Venezuela following the resumption of dialogue between the government and the opposition, is pushing to have Machado's disqualification lifted.

Venezuela has the world's largest oil reserves.

The opposition, backed by several countries including the United States, did not recognize Maduro's 2018 re-election in a vote widely dismissed as fraudulent.

The following year, Washington ramped up sanctions against Caracas that were first imposed in 2015 over the brutal repression of anti-government protests.

But the energy crisis sparked by Russia's war on Ukraine saw renewed global efforts to solve the crisis in Venezuela.

After initial talks between the government and the opposition, Washington granted a six-month license to US energy giant Chevron to operate in Venezuela.

Then, last week, the two sides agreed to hold negotiations in the second half of next year.

That was followed by Sunday's primary, for which the CNE had offered technical support, but only if it was delayed by a month.

Saab said the vote overseen by the CNP had taken place "outside the law, outside the constitution," and was "fraudulent" given that the CNE was the only body constitutionally tasked with organizing elections.

The opposition votes were cast and counted manually.

Juan Guaido, who led the opposition until late last year and lives in exile in the United States, did not stand for election in the primary.

The CNP's president and vice president as well as other commission members will be among those investigated, said Saab, to "answer for these irregularities, answer to the country and to justice."

The government has challenged the CNP's voter turnout numbers, saying they were much lower.

Machado on Tuesday insisted she would register as a presidential candidate.

"I have received a mandate from the Venezuelan people and I will execute it," she said.