The Bahrain Human Rights Centre president is already in custody, under investigation for other tweets, and risks a lengthier jail sentence.
A friend, running Rajab's account which has 261K followers, made the announcement, reposting the tweet Rajab was prosecuted for:
— Nabeel Rajab (@NABEELRAJAB) May 14, 2015 
This is the latest in a series of legal actions against Rajab, who was initially convicted of “denigrating an official body” in tweets that likened Bahrain's security apparatus to an “incubator” for fighters of the radical group ISIS. The tweet for which he was convicted suggested that Bahrain's security institutions had a number of staff that had joined terrorist groups, including ISIS.
Rajab, who heads the Bahrain Centre for Human Rights  — not recognised as a legal entity by the government — was only released from prison in May 2014 after serving two years for “disrupting public order .” That sentence came after Rajab was arrested for trying to investigate human rights violations that took place during Bahrain's popular uprising  in 2011.
On April 2, 2015, Rajab was arrested  from his home in Bani Jamra, for tweets concerning the welfare of individuals incarcerated in Bahrain's Jaw Prison as well as news about the Saudi-led coalition that has waged airstrikes against Yemen since the end of March.