Nabeel Rajab, a prominent Bahraini opposition leader, has been sentenced to three months in prison for "insulting" some Bahrainis in a tweet criticising the prime minister, Rajab's lawyer and the state news agency have said. 

Police took Rajab, the head of the Bahrain Centre for Human Rights (BCHR), into custody after the court's ruling on Tuesday, according to a colleague from the BCHR. 

Rajab, who has been a major figure in organising demonstrations during the country's 16-month protest movement, spent three weeks in jail in June under investigation after suggesting in a tweet that residents of the Muharraq district had made a recent show of support for Sheikh Khalifa bin Salman, the country's prime minister, only for financial gain. 

"A group of people from Muharraq lodged a complaint against the defendant for slandering them with insulting expressions (via publication)," the Bahrain News Agency said, citing chief prosecutor Nayef Yusuf Mahmoud.

It also said that Rajab's statements made on the social media site Twitter had cast doubt on their patriotism.

Mohammed al-Jishi, Rajab's lawyer, said the complaint was raised by a group of around 50 people, including retired army and security officers.

An official from the government's information affairs authority said the complaint was filed by two prominent residents after they were approached by the Muharraq community over what they felt were defamatory and insulting accusations.

Jishi said Rajab would lodge an appeal and that the judge had said the time Rajab had already spent in jail would count towards the sentence.

"Every day there are a thousand people insulting a thousand people; this isn't logical. Normally the charge of insult leads to just a fine. So for me it's a surprise," Jishi said.