Venezuelan President Nicolas Maduro said Thursday that he had visited Cuba and met retired leader Fidel Castro, considered one of his leftist mentors.

Maduro, whose country is facing a severe economic crisis, said his talk with the ailing Castro focused on global issues.

About 300 people gathered Wednesday to demand the release of Venezuelan opposition leader Leopoldo Lopez, one year after he was jailed for allegedly inciting mass protests against the government.

Lopez's wife, Lilian Tintori, led the rally in the same Caracas plaza where the Harvard-educated politician surrendered to security forces February 18, 2014 in the midst of a demonstration.

Venezuelan President Nicolas Maduro said Thursday that a coup being plotted by military aviation officials had been dismantled and those involved detained.

Like his predecessor Hugo Chavez, Maduro frequently announces supposed coup attempts and blames right-wing forces, as well as the United States and Colombia. 

The Venezuelan government's bank accounts at the Swiss division of HSBC, which were revealed in the "SwissLeaks" scandal, are "totally transparent," said the South American country's economy minister.

Venezuela ranked third among the countries with the largest dollar amounts in the leaked Swiss files, behind Switzerland and Britain, journalists with access to the secret documents said at the weekend.

As Venezuela's economic crisis deepens, President Nicolas Maduro has stepped up accusations of plots against his leftist government, lashing out most recently at U.S. Vice President Joe Biden.

Just ten days ago Maduro had fondly referred to Biden as "comrade," but on Sunday the Venezuelan leader was livid.

A naturalized U.S. citizen was jailed Wednesday for five years for attempting to help Venezuela build a nuclear weapon by passing on secret information, the U.S. Justice Department said.

Scientist Pedro Leonardo Mascheroni, 79, and his wife Marjorie Roxby Mascheroni, 71, had pleaded guilty after they were caught trying to pass on classified information to an FBI agent posing as a Venezuelan government official.

Venezuela, which has accused a pair of Latin American ex-presidents of trying to spark a coup, on Sunday denied them permission to speak to jailed opposition leader Leopoldo Lopez.

"Regrettably, despite all the effort we made with General Rall and even the Vice President (Jorge Arreaza), we have been denied a chance to visit Leopoldo Lopez," Chilean ex-president Sebastian Pinera said outside the Ramo Verde military prison.

OPEC is divided on how to respond to plunging crude oil prices with no plan for an emergency meeting in the next few weeks, Venezuelan President Nicolas Maduro said Tuesday.

At a meeting of the cartel in November, Venezuela unsuccessfully lobbied fellow members to tighten the taps to stem the fall in oil prices.

Jailed Venezuelan opposition leader Leopoldo Lopez said in comments published Sunday he would not accept expulsion to another country.

"That will never happen," Lopez said in a written response to questions by the Chilean newspaper El Mercurio.

Venezuelan President Nicolas Maduro has arrived in OPEC's leading oil producer Saudi Arabia, state media reported on Sunday, after he visited Iran to discuss the impact of plummeting crude prices.

Maduro landed on Saturday in Riyadh where Deputy Crown Prince Moqren bin Abdul Aziz received him, the Saudi Press Agency said.