DUBAI (Reuters) - A Bahraini appeals court on Monday lengthened the prison term imposed on Sheikh Ali Salman, leader of the main Shi'ite Muslim opposition movement, to nine years from four, his Wefaq group said.
Bahrain's public prosecutor said the stiffer sentence related to "crimes of promoting change to the political system by force", according to the Sunni Muslim-ruled Gulf Arab monarchy's state news agency BNA.
Al-Wefaq denounced the decision against Salman, a Shi'ite cleric, as "provocative" and said it undermined any chance of resolving a political crisis in Bahrain tinged with sectarianism and bitter rivalries among regional powers.
Salman was sentenced in June to four years in prison for inciting unrest. Defence lawyers appealed in September, saying that prosecutors had presented as evidence excerpts of his speeches that were taken out of context.
Prosecutors responded with their own appeal asking the court to reverse Salman's earlier acquittal on more serious charges of seeking to overthrow the political system by force, according to rights group Amnesty International.
The court extended his prison term as a result.
Salman, head of the al-Wefaq Islamic Society, was arrested in December in a case that angered his followers and stirred unrest in the kingdom, which has a Shi'ite majority.
Bahrain, which hosts the U.S. Fifth Fleet, has experienced sporadic turmoil since a Shi'ite-led uprising in 2011 that demanded democratic reforms and a bigger role in government.
That revolt was put down with military assistance from neighbouring Saudi Arabia, which fears that Shi'ite arch-rival Iran is spreading its influence in the Arab world.
(Reporting by Sami Aboudi and Noah Browning; Editing by William Maclean and Mark Heinrich)