(Adds government comment)
DUBAI, Dec 3 (Reuters) - A Bahraini court has rejected a request by a prominent human rights advocate that he be freed after serving three-quarters of a prison term for taking part in unlicensed protests.
Bahrain, where the Sunni Muslim Al Khalifa family rules over a majority Shi'ite population, has been in political turmoil since Shi'ite-led pro-democracy protests erupted in 2011.
The island kingdom is a base for the U.S. Navy's Fifth Fleet, which patrols oil shipping lanes in the Gulf region.
Lawyer Mohammed al-Jishi said rights campaigner Nabeel Rajab, sentenced last year to two years in prison for cases related to organising and participating in protests, had a legal right to early release after spending a year and half in jail.
"But the court rejected the request to release him without giving any reasons," Jishi told Reuters by telephone from Manama after Monday's ruling, which several foreign diplomats attended.
The government's Information Affairs Authority confirmed the court had deemed Rajab "not eligible" for early release.
"Rajab has continuously called upon the citizens to defy the laws of public gathering which resulted in violence," the IAA said in a statement emailed to Reuters on Tuesday.
It said many security personnel had been wounded by people throwing petrol bombs and steel rods as a result.
"Rajab's speeches included encouraging youths to confront the authorities," the IAA said. "Incitement of any sort is a violation of the constitution and laws of Bahrain that are in line with international standards."
Rajab shot to prominence in 2011 when he campaigned against a crackdown on protesters. With 217,000 followers on Twitter he is one of the Arab world's best-known online activists.
A hero to protesters but a villain to those Bahrainis who fear they will bring Shi'ite Islamists to power, Rajab is the founder of the non-governmental Bahrain Centre for Human Rights.
An organiser of many protests against the powers of the Al Khalifa dynasty, he was sentenced to three months in jail last year in a separate case over a tweet criticising the veteran prime minister, the king's uncle. The ruling was overturned, but only after Rajab had already served his sentence.
London-based Amnesty International and U.S.-based Human Rights First have called for him to be freed.
"It's depressing but no big surprise that Nabeel Rajab was not released," said Brian Dooley, of Human Rights First.
"Recent weeks have seen an increased targeting of human rights defenders by the authorities and freeing him would have gone against that trend."
Bahrain, which effectively bans protests and gatherings not licensed by the government, has been caught up in a struggle for influence between Shi'ite Iran and Sunni Saudi Arabia.
Bahrain quelled the 2011 revolt with help from Saudi Arabia and other Sunni-ruled Gulf states, but protests and small-scale clashes persist and bomb attacks have multiplied since mid-2012.
Talks between the government and opposition have failed to end the political standoff. Many Shi'ites complain of political and economic discrimination, a charge the authorities deny. (Reporting by Rania El Gamal; Editing by Alistair Lyon)