Kuwait's supreme court Sunday upheld a two-year jail sentence handed to an opposition online activist for writing tweets deemed offensive to the Gulf state's ruler.

Hejab al-Hajeri, a student of law in his early 20s, said on his Twitter account after the ruling that his "determination is bigger than their jail."

Hajeri was handed the jail term by the emirate's lower court in April last year after it deemed that comments he made on his Twitter social network account were critical of the emir.

The appeals court upheld the sentence six months later.

The activist, who has been out on bail, must now serve the jail term since the supreme court's verdicts are final.