Bahrain's highest court upheld on Monday the prison sentences of 13 leaders of a 2011 uprising, a defense lawyer said, in a ruling that could stir further unrest in the US-allied Gulf Arab state.

Bahrain, where the US Fifth Fleet is based, has been in political turmoil since a protest movement led by majority Shi'ite Muslims erupted in February 2011 during a tide of revolts against governments across the Arab world. Bahrain accuses Shi'ite power Iran of encouraging the unrest.

The sentences handed down by a military court in June 2011 and upheld by a civilian court in September last year range from five years in prison to life.

"This verdict is final. No more appeals are possible," lawyer Mohammed al-Jishi  told Reuters by telephone from Manama.

Bahrain's main opposition group, Al Wefaq, condemned Monday's decision. "These judgments confirmed the rulings issued before by the military court which were condemned by the whole world. I think it is accurate to call these rulings political persecution," Wefaq leader Sheikh Ali Salman told Reuters.

The US government criticized the ruling.

"We regret today's decision," State Department spokeswoman Victoria Nuland told reporters in Washington. "We're concerned that this decision further restricts freedom of expression and compromises the atmosphere within Bahrain for reconciliation."

Reuters