A Saudi court sentenced a man to 10 years in jail and a 100,000 riyal ($26,700) fine for joining protests against the kingdom's rulers and using Twitter to urge people to do the same, state news agency SPA said on Monday.
SPA quoted Justice Ministry spokesman Fahd al-Bakran as saying the unidentified defendant had also retweeted messages against the monarchy, Muslim scholars and security services.
"(He was) convicted of entering an Internet site hostile to the state that encourages fighting and promotes deviant thought," Bakran said, referring to al Qaeda ideology.
The man, who has been in jail for three years, was charged and convicted under laws that criminalise internet abuse.
The verdict was announced two days after Saudi Arabia designated the Muslim Brotherhood, the Nusra Front and the Islamic State in Iraq and the Levant as terrorist organisations.
The decree applies to Saudis and foreign residents who join, endorse or give moral or material aid to groups classified as terrorist or extremist, whether inside or outside the country.
The Brotherhood renounced violence decades ago, unlike the other two banned groups, which are inspired by al Qaeda.
Saudi Arabia recently ratified an anti-terrorism law that rights campaigners have criticised as a tool to stifle dissent.
In a separate case, the court sentenced another defendant to eight years in jail for contacting a man wanted by security forces and trying to help people wounded during demonstrations.
He was also charged with joining a funeral procession for a person killed during unrest in Saudi Arabia's mostly Shi'ite Eastern Province and with chanting anti-government slogans.
Minority Shi'ites have staged sporadic protests in Qatif since 1979. The town's most recent wave of demonstrations began during the Arab uprisings of 2011 and continued through 2012.
At least 21 people have been shot dead in the region since early 2011. Shi'ites say they suffer persistent discrimination in the Sunni-ruled kingdom, a charge the authorities deny. ($1 = 3.7503 Saudi riyals)