Amnesty International on Wednesday called on Bahraini authorities to release leading Shiite activist Nabil Rajab sentenced to three months in jail for posting tweets deemed insulting to Sunnis.
"Like many others in Bahrain, Rajab is a prisoner of conscience, jailed solely for peacefully exercising his right to freedom of expression," said Ann Harrison of Amnesty's Middle East and North Africa programme.
"He should be released immediately and all other charges or convictions against him dropped or overturned," she added.
Rajab was sentenced on Monday.
He had been released on June 27, three weeks after he was arrested for tweeting insults against the predominantly Sunni population of the province of Muharaq, according to prosecutors.
In a statement last month, prosecutors said they received complaints that Rajab "talked on social networks about the people of Muharaq in a way that questioned their patriotism and insulted them."
Last year, a significant part of the minority Sunni community rallied around the government as Shiites led protests against the regime of the country's Sunni monarchy.
Rajab is on trial in three other cases, all of which are linked to separate protests across Bahrain.
The activist had led anti-government protests following a government crackdown on Shiite-led demonstrations against the regime in March 2011.
Amnesty says 60 people have been killed since the protests erupted in February last year in the Gulf kingdom ruled by the Al-Khalifa family.