Bahrain released one of the Arab world's best-known activists on Saturday after he served a two-year jail sentence for his role in protests calling for democracy in the U.S.-allied kingdom.

Nabeel Rajab, founder of the Bahrain Center for Human Rights, was found guilty in August 2012 of organizing and participating in illegal protests to push for reforms in the Sunni Muslim-ruled kingdom.

Speaking after his release, Rajab said he had been shocked at how the situation in Bahrain had worsened during his time in prison. Authorities had been targeting activists and human rights advocates, he said. "I will continue to struggle for democracy and for respect for human rights," he said.

Bahrain, a base for the U.S. Navy's Fifth Fleet, has been in turmoil since protests led by Shiite Muslims erupted in 2011 after similar uprisings in Egypt and Tunisia.

Talks between the government and opposition have failed to end the political standoff. Many Shiites complain of political and economic discrimination, a charge the authorities deny.