Maria Corina Machado, who backed anti-government protests this year, charged over alleged plot to kill president Maduro.
Jailed Venezuelan opposition leader Leopoldo Lopez has been sentenced to more than 13 years in prison, his lawyer Roberto Marrero has said.
The popular dissident, a US-trained economist who has been held at a military prison since February 2014, is accused of inciting violence against the government of President Nicolas Maduro and attempting to force his ouster.
A court in Caracas, the capital, found Lopez guilty late on Thursday for his role as the leader of a street protest movement which was involved in bloody clashes with security forces in February last year.
The sentence was for 13 years, nine months and seven days.
He will serve out his sentence in the military prison of Ramo Verde, where he has been held since he turned himself in shortly after the protests.
“If the sentence condemns me you will be more fearful to read it than I will be to hear it, because you know that I’m innocent,” Lopez defiantly told the judge according to a witness, David Smolansky.
Smolansky, a Caracas neighbourhood mayor who was at the closed-door hearing, described Lopez’s appearance via Twitter.
Fighting broke out earlier in the day between supporters of Lopez, 44, and pro-government demonstrators outside the courthouse.
Wielding sticks and plastic bottles, supporters of socialist Maduro’s government descended on a group of Lopez’s followers who had been waiting since the early hours of the morning for the final phase of his trial, an AFP news agency correspondent said.
— 24 Horas (@24HorasTVN) September 11, 2015
Lopez supporters said one of their activists had died of a heart attack during the scuffle – a claim that could not be independently verified.
The police and national guard later intervened to keep the two groups apart.
Last year’s protests erupted in response to violent crime, a sinking economy and severe shortages of basic goods.
Between February and June last year, 43 people were killed in protest-related violence.
Lopez was arrested on February 18, 2014, handing himself in to police after giving an impassioned speech to his supporters.
In May, the opposition leader staged a month-long hunger strike to pressure authorities to set a date for legislative elections.
He ended the strike after the vote was set for December 6.
Venezuela remains polarised between government supporters, who see the ruling socialist government as a bulwark against neo-liberal economics and US imperialism, and those in opposition who see Maduro’s rule as increasingly autocratic and incompetent.
Opinion polls indicate Maduro’s movement risks losing for the first time since his late mentor Hugo Chavez came to power in 1999.