Ibrahim Sharif, who headed the opposition group Waed, was freed on June 19 after spending four years in jail over involvement in 2011 pro-democracy protests against Al-Khalifa regime, Al-Manar reported.

But he was re-arrested three weeks later for "violating the law".

Al-Wasat Bahraini daily said the public prosecution referred Sharif to trial on August 24.

For his part, Public Prosecutor Wael Buallay said, in a statement carried by state news agency BNA, an unnamed individual was accused of "promoting political change through forceful means and threats and inciting hatred against the political regime".

Judicial sources in Bahrain confirmed that the statement, which gave an August 24 date for the trial to open in the Higher Criminal Court, was referring to Sharif.

Sharif was among a group of 20 activists tried for "plotting to overthrow" the rulers of Bahrain.

Opposition sources say the activist was taken back to prison after he criticized the government during a ceremony for a victim of the unrest that has rocked the kingdom.