A lower criminal court in Bahrain, headed by a member of the ruling family, has sentenced a 17-year-old boy to a year in jail for insulting the Gulf island's king on Twitter.

The Bahrain Centre for Human Rights (BCHR) on Saturday said Ali Al Shofa was arrested in a house raid at dawn on 12 March 2013. He spent two months in jail while under investigation.

Ali was accused of posting insulting comments about Sheikh Hamad Al-Khalifa using the account @alkawarahnews, which he denied a relationship with. His lawyer submitted evidence that the account was still being run by other people.

Human rights groups said the sentencing was part of a wider crackdown on freedom of speech in Bahrain.

Last month a court sentenced five twitter users to a year each in jail for insulting the king on twitter.

Earlier in June, the BCHR reported the abduction and incommunicado detention of Jaffar Al-Demstani for tweeting about the torture of his father, Ebrahim Al-Demstani.