Image caption Somyot Prueksakasemsuk had launched a petition against the laws he was found to have broken

A Thai court has jailed a magazine editor for 10 years for publishing articles that were deemed to have insulted the monarchy.

Somyot Pruksakasemsuk, who is also a prominent political activist, was sentenced in connection with two articles in the magazine.

He was prosecuted under Thailand's lese majeste law, which campaigners say is being used to curb free speech.

Rights groups and the European Union have condemned the verdict.

The European Union said it "seriously undermines the right to freedom of expression and press freedom".

"At the same time, it affects Thailand's image as a free and democratic society," AFP quoted the EU's delegation in Bangkok as saying.

'Regressive'

Somyot and the magazine he edited were closely aligned with Thailand's "red-shirt" movement, which led anti-government protests in 2010 that shut down parts of Bangkok.

He had been detained without bail since April 2011 and his supporters have complained that he has been mistreated in custody.

The two articles in question were published in 2010 under pseudonyms in the magazine that he founded.

Somyot was arrested a year later, five days after launching a petition calling for a review of Article 112, which says those who defame the monarchy face jail.

The court handed him five-year terms for each magazine article, with an additional year added from a suspended defamation case from three years ago.

His lawyer said he would appeal.

Image caption Thailand's lese majeste laws are intended to protect the monarchy

The BBC's Jonah Fisher in Bangkok says the severity of the sentence has shocked many in Thailand.

Thailand's lese majeste laws are intended to protect the monarchy, headed by 85-year-old King Bhumibol Adulyadej, but critics say they have been increasingly politicised.

Brad Adams, Asia director at Human Rights Watch, said the ruling "appears to be more about Somyot's strong support for amending the lese majeste law than about any harm incurred by the monarchy".

Amnesty International described the ruling as "regressive".

"Authorities in Thailand have in recent years increasingly used legislation, including the lèse majesté law, to silence peaceful dissent and imprison prisoners of conscience," said the group's deputy Asia-Pacific director Isabelle Arradon.

"The lese majeste law should immediately be suspended and revised so that it complies with Thailand's international human rights obligations."

Earlier this month activist and comedian Yossawaris Chuklom, a "red-shirt" supporter, was jailed for two years under the laws for a speech he made at a rally in Bangkok during the 2010 "red-shirt" political protests in Bangkok.