Activists planned new protests in Venezuela on Friday after jailed opposition leader Leopoldo Lopez was sentenced to nearly 14 years in prison for inciting violence during deadly anti-government protests in 2014.
After the court decision against the popular, US-trained economist, the opposition called for "peaceful" protests.
"We call for protests to take place in a peaceful, democratic and constitutional way," said Jesus Torrealba, executive secretary of the opposition coalition Democratic Unity Roundtable.
Lopez will serve his time at the Ramo Verde military prison, where he has been held since February 2014.
Judge Susana Barreiros found Lopez guilty of "damage and arson, public incitement and conspiracy," the attorney general's office said.
He was jailed for 13 years, nine months and seven days, defense lawyer Roberto Marrero said late Thursday on Twitter.
The opposition rejected the ruling, proclaimed Lopez's innocence and called the sentencing decision a political, not a judicial one.
Another Lopez attorney, Juan Carlos Gutierrez, said the trial was plagued with irregularities, reflecting the "lack of independence" of the Venezuelan judicial system.
Lilian Tintori, Lopez's wife with whom he has two children, urged her husband's supporters to gather Friday in a square in eastern Caracas to repudiate the ruling.
"Today, it has been confirmed once again that we live in an undemocratic, corrupt and inefficient regime. After this unjust sentence, we will continue to fight," she told dozens of angry supporters.
The sentence was also condemned by the European Commission, former Colombian president Andres Pastrana and Human Rights Watch Americas director Jose Miguel Vivanco.
The trial of Lopez and four students "have failed to provide the defendants with adequate guarantees of transparency and due legal process," the European Commission said in a statement.
"The EU hopes that the avenues available for redress will allow to review these harsh verdicts in a fair and transparent manner."
It noted that local security forces prevented diplomats and other independent observers from attending the end of the trial, even though the judge had granted authorization.
Scores of members of Lopez's center-right party held a vigil in the Caracas neighborhood of Chacao. Several women burst into tears upon hearing the verdict.
Reports quickly surfaced on social media of heavy pot-banging -- a popular sign of anger -- in downtown Caracas in opposition to the ruling.
Supporters of Lopez, 44, said one of their activists had died of a heart attack during a scuffle with pro-government supporters -- a claim that could not be independently verified.
The police and national guard later intervened to keep the two groups apart.
True to his provocative style, Lopez spoke out during the closed-door hearing to which the press had no access, launching a challenge against the judge, according to members of Lopez's Popular Will party.
"If the sentence condemns me, you will be more afraid to read it than I will be to hear it, because you know that I'm innocent," Lopez defiantly told the judge according to David Smolansky, a Caracas neighborhood mayor who was at the hearing.
Fighting broke out earlier in the day between supporters of Lopez and pro-government demonstrators outside the courthouse.
Wielding sticks and plastic bottles, red-shirted supporters of socialist President Nicolas 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.
"Statements made by Lopez through the media and social networks incited his followers to violence in the streets and ignore the national government and the institutions of the Venezuelan state," the attorney general's office said.
The charges against Lopez are linked to protests against the Maduro administration in which 43 people died and some 3,000 were wounded between January and May 2014.
The first reaction by a government official came from Correctional Services Minister Iris Varela, who tweeted: "No to impunity and no justice for the cheap monster... He was responsible for 43 victims who now rest forever because of his fascist adventure."
The courtroom session began at noon and went into the night because three other people, all students, were also being tried.
One was sentenced to 10 years in prison for participating in the riots, and the other two got four years each.
The calm that reigned in the morning around the Supreme Tribunal of Justice gave way to clashes between members of Lopez's party and pro-government supporters.
At least four journalists were attacked during these incidents, including two whose equipment was stolen, according to the National Union of Press Workers.