Venezuela's military on Thursday arrested the country's former oil minister and the ex-chief of state oil company PDVSA after both men were sacked as part of an anti-corruption crackdown.

Attorney General Tarek William Saab told journalists that the former minister Eulogio del Pino and ex-PDVSA boss Nelson Martinez were picked up in a dawn operation by the country's Military Counterintelligence Unit.

Both former officials were arrested at their homes, four days after they were axed from their jobs by President Nicolas Maduro.

The Venezuelan leader supported the operation and warned that "whoever violates his oath of loyalty and violates the trust placed in him... will be persecuted and punished," Communications Minister Jorge Rodriguez said on Twitter.

State television images showed black-clad security forces, their faces covered and armed with rifles, knocking on the door of Del Pino's apartment.

When he emerged, dressed in shorts and a Venezuela football shirt, the powerful former official was handcuffed and later fingerprinted.

Saab said Del Pino was accused of "intentionally altering oil production figures" and said the arrests were part of an operation "to dismantle the cartel that has been hitting the oil industry."

But in a video Del Pino recorded before his arrest, which was made available on Twitter, he called charges against him an "unjustified attack" and demanded that he be assured of the right to respond to the accusations.

Martinez was charged in connection with alleged fraud at PDVSA's US-based affiliate Citgo.

Saab said he also had ordered the arrests of 16 people as part of the operation, some of whom were "outside the country," adding: "We hope they will be delivered to Venezuelan justice."

- 'Sabotage' -

Del Pino and Martinez are the highest-ranking officials arrested as part of an anti-corruption purge at PDVSA, the state oil giant that accounts for almost all the country's income.

Oil minister Manuel Quevedo, a former general installed to replace both men, told reporters at an OPEC meeting in Vienna that Venezuela's oil production was being sabotaged as a preamble to a coup.

"This sabotage plan is aimed at achieving a repeat of 2002-03 when there was an attempted coup" against former president Hugo Chavez, Quevedo said.

Last week, the Venezuelan authorities arrested six Citgo executives for allegedly signing contracts to refinance $4 billion in debt without government approval. The government alleges that a $50 million bribe was paid as part of that deal.

- Aggressive push -

Thursday's arrests come amid what analysts say is an aggressive push by Maduro to consolidate power over the country's key institutions and increasingly scarce resources ahead of next year's election.

Key targets in the purge are allies of Venezuela's UN ambassador Rafael Ramirez, to whom both men arrested Thursday were close.

Ramirez, who led PDVSA for a decade, is himself rumored to be on borrowed time in his UN post.

"While it may be that Ramirez has yet to be formally notified, he will probably be out in a matter of days," said Eurasia Group analyst Lisa Grais-Targow.

"The targeting of Ramirez is part of a broader effort by Maduro to consolidate his control over key institutions, including PDVSA, and to ensure that the military is fully bought into his political survival," she said.

At least one-third of Venezuela's cabinet is made up of active or retired officers, and the military has become a major pillar of support for the widely unpopular socialist leader.

Analyst Axel Capriles said that the arrests went beyond the crusade against corruption to reflect a power struggle going on for control of the political legacy of Chavez, who died in 2013 having chosen Maduro as his political heir.

"It's a confrontation between the beneficiaries of corruption, an internal war between revolutionary mafias to demarcate what is left of the booty," Capriles said on Twitter.

The South American country, teetering on the brink of a full-blown default on its massive debt, has the world's biggest reserves of oil.

But because of endemic corruption and a chronic lack of investment, the OPEC member's production is falling sharply.

Annual output is around 1.9 million barrels per day, having slumped more than 23 percent between January 2016 and October this year.