Prominent Shi'ite activist Nabeel Rajab has been sentenced to six months in prison after a Bahraini court found him guilty of insulting public institutions in his tweets, a judicial source says.
But Rajab, who was released from custody one month after his arrest on October 1, could stay out of prison on bail if he pays 200 dinars ($A570 dollars), a judicial source told AFP, citing the court ruling.
Condemned by Amnesty International as "a blow to freedom of expression", the decision is subject to appeal, according to the prosecution.
Rajab, a member of Bahrain's Shiite majority, which has held protests against the kingdom's Sunni rulers since 2011, was arrested after posting comments on Twitter about the interior and defence ministries.
In one of the messages deemed offensive, Rajab charged that many Bahrainis fighting with jihadists in Syria were former Bahraini security forces personnel who had developed Sunni extremist views while in service.
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Rajab, who has led anti-government marches and heads the Bahrain Centre for Human Rights, was freed last May after serving two years in jail for taking part in unauthorised protests.
His new conviction came one day after prosecutors charged Bahrain's Shi'ite opposition chief Sheikh Ali Salman with attempting to overthrow the regime and set a January 28 trial date.
International rights groups have condemned the trials against opponents of the Sunni regime ruling the Gulf state.
"Nabeel Rajab is being unjustly punished simply for posting tweets deemed insulting to the authorities. His conviction is a blow to freedom of expression - it must be quashed," said Amnesty's Said Boumedouha, urging his immediate and unconditional release.
