BEIJING (Reuters) - A Chinese court sentenced Chinese-born Swedish citizen Gui Minhai to 10 years in jail on Monday for illegally providing intelligence overseas, prompting a protest from Stockholm.

Gui, a bookseller previously based in Hong Kong who sold books critical of China’s political leadership, was detained by mainland police in 2018. He was seized while with Swedish diplomats on a Beijing-bound train.

Relations between Sweden and China soured in the months leading up to Monday’s sentencing, with Chinese officials warning Swedish counterparts against meddling in China’s internal affairs.

On Tuesday, Sweden summoned the Chinese ambassador to Stockholm to protest against the sentence and demand Gui’s release.

“We have summoned China’s ambassador to our cabinet secretary and again demanded the release of, and consular access to, our citizen,” a foreign ministry spokesman told Reuters.

Earlier on Tuesday, Swedish foreign minister Ann Linde said Gui should be released, a position Sweden has held throughout.

“We also require access to our citizen to provide the consular support he is entitled to,” Linde said.

“We have not had access to or knowledge of any trial. Thus, we have not been able to review the indictment nor been able to offer access to legal counsel,” she said.

A statement by the Ningbo Intermediate People’s Court, which jailed Gui, said the 55-year-old had stated that he would not appeal the sentence and had asked to have his Chinese citizenship reinstated.

A spokesman for China’ foreign ministry told a news briefing that Gui’s rights and interests had been fully guaranteed. He said consular visits in general were put on hold due to the coronavirus outbreak.

Chinese officials objected to Svenska PEN, a literary organisation, awarding Gui the 2019 Tulcholsky Prize, praising his services to free speech.

Swedish culture minister Amanda Lind defied Chinese diplomatic threats of “countermeasures” to present the prize.

Gui is the highest-profile of five booksellers who disappeared between October and December 2015, all linked to a Hong Kong bookshop known for its gossipy texts on Chinese political leaders.

Such books are banned on the mainland but their production and sale is legal in Hong Kong under freedoms guaranteed as part of the 1997 handover from British colonial rule to Chinese sovereignty.

Gui was initially abducted in the Thai beach resort of Pattaya in 2015 before surfacing, like the others, in detention in mainland China. He was released in October 2017, before being arrested in January 2018.

Three of his colleagues were detained in mainland China while another was widely thought to have been abducted in Hong Kong and spirited across the border. Gui is the only one to have remained in detention.

His daughter Angela, along with other supporters, has repeatedly called for his release, saying he is a victim of illegal political persecution.