The main Shia opposition leader in Bahrain, Sheikh Ali Salman, has been jailed for four years for inciting violence, state media say.
Sheikh Salman was convicted of inciting hatred, promoting disobedience and "insulting" public institutions.
His al-Wefaq movement has accused the Sunni-led government of aggravating the country's crisis with his sentencing.
The Gulf state has grappled with sporadic unrest since putting down mass Shia-led protests in 2011.
Campaign group Amnesty International said the conviction violated the International Covenant on Civil and Political Rights, to which Bahrain is a signatory.
Sheikh Salman's arrest in December triggered protests across the country.
"The regime is pushing toward aggravation and issued a sentence of four years for the Bahraini opposition leader Sheikh Ali Salman," al-Wefaq tweeted.
Bahrain's state news agency BNA said Sheikh Salman had been found guilty of charges "relating to publicly inciting hatred, an act which disturbed public peace, inciting non-compliance with the law and insulting public institutions".
But he was acquitted of inciting political change by force, for which he could have been jailed for life.
The charges relate to a series of statements by Sheikh Salman made in a public speech last year.
Said Boumedouha, Middle East and North Africa deputy director at Amnesty, called the conviction "shocking".
"It is yet another clear example of Bahrain's flagrant disregard for its international obligations," Mr Boumedouha said.
"Sheikh Ali Salman has been sentenced solely for peacefully expressing his opinion," he added.
His defence lawyer, Abdullah al-Shamlawi, has said that Sheikh Salman can appeal Tuesday's verdict.
Shia-dominated demonstrations against the Sunni monarchy have been continuing sporadically for the past four years.
In 2011, dozens died when the government moved to quash protests. The demonstrators were demanding more rights and an end to discrimination against the majority Shia community by the Sunni royal family.