An Omani court on Monday sentenced four pro-reform activists to jail terms of between six months and a year for defaming Sultan Qaboos, their lawyer said, but they were freed on bail pending an appeal.

Hamad al-Kharusi, Ali al-Meqbali and Mahmoud al-Rawahi were sentenced to one year in prison for lese majeste, defaming the sultan, and for "violating the law on cyber crimes," said one of their lawyers, Yaqub al-Kharusi.

Hammoud al-Rashidi was handed a six-month term for the same offence, he told AFP.

The four defendants were released on bail of 1,000 Omani riyals (2,600 dollars) each pending the appeal.

They are among a group of 36 pro-reform activists that includes bloggers, writers and lawyers arrested for anti-government actions at the start of June. They have all been released, some of them on bail.

Paris-based watchdog Reporters without Borders and New York-based Human Right Watch have denounced the arrests.

Oman was hit by a wave of protests last year demanding political reforms and riot police dispersed the demonstrations with force.