HONG KONG — A court in China has given a 10-year prison sentence to a Hong Kong publisher who had been working on a book critical of Chinese President Xi Jinping.

Yao Wentian, who has printed several books that are banned in mainland China, was arrested in Shenzhen last year on charges of smuggling chemicals across the border. His arrest came as he was preparing to publish a book by exiled dissident writer Yu Jie titled “China’s Godfather: Xi Jinping.”

His son, Yao Yongzhan, told VOA’s Mandarin service that his 73-year-old father’s conviction is unjust.

“When I heard this news, of course I was shocked,” he said. “My father is pursuing freedom. This is the price he has to pay for the country. I still hope he will be released as early as possible. We will appeal. I believe he is innocent.”

Yao Wentian’s lawyer, Ding Xikui, told VOA that his client, who is also known by the name Yiu Mantin, was only an accomplice and the sentence was too heavy. Critics of the Chinese government have accused authorities of targeting Yao because of his publishing activities.