A lawyer for a prominent Bahraini rights activist says an appeals court has upheld a verdict against Nabeel Rajab for insulting government ministries on Twitter.

Lawyer Jalila al-Sayed said Rajab will seek to have the case overturned by the court of cassation, the last court of appeal. Rajab remains jailed pending an investigation on separate charges related to online comments.

Thursday's appeals court decision relates to a January verdict against Rajab, who was sentenced to six months in prison for insulting the ministries of defense and interior in tweets alleging that Bahrain's security institutions were incubators for extremist ideology.

The tiny island nation of Bahrain has faced four years of unrest led by its majority Shiites calling for greater political rights from the Sunni leadership.