A prominent opposition leader in Venezuela has been charged with involvement in an alleged plot to assassinate socialist President Nicolas Maduro.

Maria Corina Machado, a vocal supporter of anti-government protests that rocked the country earlier this year, rejected the charge as she left the attorney general's office after questioning on Wednesday.

"Today they have charged me with the crime of conspiracy," Machado said as she left attorney general's office in the capital, Caracas, flanked by her supporters and the leader of the main opposition coalition, Jesus Torrealba.

"All the accusations and supposed evidence are false, and I reject them," she added.

The charge carries a maximum of 16 years in prison.

Her case will now be assigned to a judge who will formally charge Machado, a former member of the National Assembly, and decide whether she should be detained pending trial.

The attorney general's office said in a statement that she had been charged with "conspiracy" for "allegedly having links to the assassination plan against the president".

'Assassination plot'

Maduro, who succeeded the late Hugo Chavez last year and has come under mounting political pressure as the country's oil-based economy sours, has made frequent claims of plots against him.

Machado, 47, who says the evidence against her amounts to slander, was ousted from her seat in the National Assembly in March.

Along with Leopoldo Lopez, an opposition leader jailed since February on charges of inciting violent protests, she has been one of the most visible figures in an anti-government protest movement called "La Salida," or "The Way Out".

The movement seeks to use street protests to press for Maduro's resignation.

In May, ruling party leaders made public emails that they claimed showed Machado was plotting against Maduro with others, including the US ambassador to Colombia, Kevin Whitaker.

The opposition and human rights groups have accused the government of using the judicial system to persecute dissidents.

The US government has voiced concern and dismissed tha charges against Machado as a ploy to intimidate the opposition.

"We are deeply concerned by what appears to be the Venezuelan government's continuing effort to intimidate its political opponents through abuse of the legal process," said State Department spokeswoman Marie Harf.

Other opposition leaders rushed to her defence, including Henrique Capriles, the candidate who narrowly lost to Maduro in presidential elections last year.

Capriles dismissed the case against Machado as "a little circus put together by Nicolas (Maduro)".

Source: Agencies