Reuters: Bahrain sentenced opposition leader Sheikh Ali Salman to four years in jail on Tuesday on charges of inciting unrest, his supporters and government officials said.

Salman is the most senior figure in the Sunni Muslim-ruled kingdom's Shi'ite opposition to be jailed since anti-government protests erupted in 2011, at the height of the region's "Arab Spring" uprisings.

"The high criminal court today issued a ruling of imprisonment for 4 years against the secretary general of a political society," the public prosecutor said on its official Twitter account.

Salman, who was not named in the statement, was convicted on charges of "explicit incitement against a group of the people, including disturbing the public peace and explicit incitement toward disobeying the law," according to the prosecutor.

The al Wefaq Islamic Society headed by Salman, a 49-year old Shi'ite cleric, confirmed he had been sentenced and condemned the ruling.

"The regime is pushing toward aggravation and issued a sentence of four years for the Bahraini opposition leader Sheikh Ali Salman," the party wrote on its Twitter account.

Bahrain, which hosts the U.S. Fifth Fleet, has experienced sporadic turmoil since the mass protests in 2011 led by majority Shi'ites demanding reforms and a bigger role in government. That uprising was put down with military help from Saudi Arabia.

The island kingdom says it has made significant political reforms and increased oversight of security forces. Opponents say abuses continue.

With a political accord between the government and opposition remaining elusive, there has been an increase in deadly bomb attacks on Bahraini security forces.

Amnesty International called on Bahrain on Monday to free Salman, calling him a "prisoner of conscience" and saying he had not received a fair trial.

The prosecution accused Salman of promoting the overthrow of the political system by force, inciting violence and supporting attacks that caused the deaths of 14 policemen. He denies the charges and has dismissed the trial as bid to muzzle dissent.

In a statement on Monday, the government said the "serious charges" against Salman were rightly regarded as a criminal offence, and that he had received a fair trial.

"Ali Salman's case relates to criminal charges, specifically incitement of hatred, as well as inciting violence. The charges and subsequent trial are wholly unrelated to any political views he may hold," the government statement said.