A Chinese court has sentenced defence lawyer Xia Lin to 12 years in prison, his attorney said Thursday, the latest blow in a broad crackdown on human rights defenders and activists.

Xia is best known for his work defending artist Ai Weiwei and fellow rights lawyer Pu Zhiqiang, who was detained after a private seminar discussing the 1989 Tiananmen Square crackdown.

"The court sentenced Xia Lin to 12 years in prison for fraud," his lawyer, Dong Xikui, told AFP.

Police detained Xia in November 2014, and later charged him with fraudulently obtaining 100 million yuan ($15 million) to pay off gambling debts, according to a defence statement.

His trial opened in Beijing in June of this year.

"We pleaded not guilty, but the court adopted only part of our defence opinion and reduced the amount of fraud from more than 100 million down to 48 million," his lawyer said.

Chinese President Xi Jinping has overseen a tightening of controls on civil society since assuming power in 2012, closing avenues for legal activism that had opened up in recent years.

While the government initially targeted political activists and human rights campaigners, it has increasingly turned its attention to the legal professionals who represent them.

In the most striking example, authorities detained more than 200 people last year during the so-called "709 crackdown" -- named after the July 9th date of the roundup -- including lawyers who took on civil rights cases considered sensitive by China's ruling Communist party.

Pu, the lawyer detained over the Tiananmen event, received a three-year suspended prison term last December for "inciting ethnic hatred" and "picking quarrels and provoking trouble" in a case that drew international condemnation.

Xia's sentence was unusually tough, according to Maya Wang, an Asia researcher at Human Rights Watch, and will "send a deep chill through the community of human rights lawyers who have been under a sustained crackdown under President Xi's government in the past year".

"The sentence is shocking, not only because of its length, but also because it was handed down to a rights lawyer who has tried to protect himself by deliberately taking a low-profile, technical approach to his work."