Bangkok, Thailand (CNN) -- A Thai court on Wednesday sentenced a political activist to 10 years in prison for insulting the country's revered king, a decision that drew criticism from human rights groups and the European Union.
The Criminal Court in Bangkok ruled that Somyot Pruksakasemsuk had breached Thailand's strict lese majeste laws when a magazine he edited, Voice of Thaksin, published two satirical articles found to be critical of the monarchy.
Somyot, who arrived in court barefoot with shackles around his ankles, plans to appeal, according to his lawyer, Karom Polpornklang.
"The verdict seriously undermines the right to freedom of expression and press freedom," The European Union said in a statement. "At the same time, it affects Thailand's image as a free and democratic society."
Thai laws allow courts to hand down lengthy prison terms to people convicted of defaming, insulting or threatening the royal family.
Before his detention began in April 2011, Somyot had campaigned to change the lese majeste law. And he submitted a petition to the Thai Constitutional Court while he was in jail, arguing the law goes against basic human rights and the punishment it permits is not proportionate.
Authorities have held him in jail since his arrest, denying repeated bail requests.
"The court's ruling appears to be more about Somyot's strong support for amending the lese majeste law than about any harm incurred by the monarchy," said Brad Adams, Asia director for Human Rights Watch.
Somyot also received a further one-year sentence Wednesday for a previous suspended sentence for defamation, bringing his total prison term to 11 years.
More than 20 diplomats, many of them European, attended the hearing, along with about 20 of Somyot's supporters, at whom he smiled as he left the courtroom.
Somyot's magazine published the controversial articles in 2010, during severe political unrest in Bangkok. He was a member of the Red Shirts, a group that held anti-government protests and clashed with Thai security forces.
The Red Shirts support former Prime Minister Thaksin Shinawatra, who was ousted in a bloodless military coup in 2006.
It is not possible to report details of the content of the articles in question since they have been deemed to violate Thai law.
Thailand's King Bhumibol Adulyadej, 85, is the world's longest reigning monarch.
The country abolished absolute monarchy in the 1930s, and the king wields little political power. Still, the king -- formally crowned on May 5, 1950 -- is a deeply respected figure in Thailand and enjoys widespread popularity.
Human Rights Watch says there was a sharp increase in the number of lese majeste cases brought to trial in Thailand between January 2006 and May 2011.
Prosecutions have since decreased under Prime Minister Yingluck Shinawatra, Thaksin's sister who took office in 2011.
But authorities "continue to use draconian statutes in the Penal Code and the Computer Crime Act to restrict freedom of expression, including on the Internet," Human Rights Watch said.
Last year, a web editor received a 20,000 baht (US $628) fine and an eight-month suspended sentence for not deleting posts deemed critical of the monarchy quickly enough.