Dubai: An Omani court jailed a prominent activist for three years on Sunday for a range of offences including undermining the state, a charge a newspaper said was related to an open letter to US President Barack Obama about human rights in the country.

Western-allied Oman, which experienced Arab Spring protests in 2011, has tried to clamp down on public dissent, arresting rights activists who criticise authorities on social media.

Lawyer Yaboub Al Harthi said the Court of First Instance in Muscat had found Said Jadad, who took part in the 2011 protests, guilty of “undermining the prestige of the state”, inciting the public to join an illegal gathering, and using the internet to publish materials that disturb public order.

As well as the jail sentence, Jadad was also ordered to pay fines totalling 1,700 rials (Dh16,218). The court set a 2,000 rial bail for any decision to free him pending an appeal.

The lawyer said Jadad intended to appeal against the ruling.

Omani online newspaper Mowatin said the charge of undermining the state stemmed from a 2013 open letter to Obama, in which Jadad had expressed “dismay” over the US’ policies regarding human rights in the Gulf.

“We expect the United States, being a superpower, to always stand by the people and to support the principles of democracy and human rights,” he wrote.

The newspaper said Jadad’s lawyer had argued in court that the message came under the right to freedom of opinion and expression, and that the accused had personally suffered from human rights abuses, including being detained for seven days without a warrant and having his documents seized without a court ruling.

The Monitor of Human Rights in Oman, in a report on human rights abuses in 2014, said a number of activists had been detained. They included Talib Al Maamari, a member of Oman’s Shura council, a consultative body, who was then jailed for four years for undermining the state and other offences.