A second Kuwaiti man has been sentenced to two years in jail for insulting the emir on Twitter as the Gulf Arab state tightens its grip on social media criticisms of the establishment.

Ayyad al-Harbi was found guilty of undermining the status of the Sheikh Sabah al-Ahmad al-Sabah.

The same court sentenced Rashid Saleh al-Anzi to two years in jail on Sunday on the same charges.

According to the verdict, published by online newspaper Alaan, a tweet by Anzi in October "stabbed" the rights and powers of the emir. It is illegal to criticise the emir in Kuwait on the grounds of state security.

Anzi, who has 5,700 Twitter followers, was expected to appeal, his lawyer said.

Kuwait, an ally of the US and major oil producer, began a clampdown on tweeters, activists and opposition lawmakers ahead of elections in December.

The opposition has staged regular protests against an amendment of the electoral law. Members of the ruling family hold the top posts in the hand-picked government.

Hundreds of demonstrators held a rally on Sunday to demand the dissolution of parliament and the scrapping of the controversial amendment. More than 70 activists were arrested and police fired teargas and stun grenades to disperse the crowd.

Mohammed al-Humaidi, head of Kuwait Society for Human Rights, told AFP that more than 200 opposition activists face trial on a variety of charges, mainly for criticising the emir.