BEIJING (AFP) - Chinese authorities have detained the brother-in-law of jailed Nobel Peace Prize laureate Liu Xiaobo on a fraud charge, his lawyer said on Friday.

Police detained Liu Hui in January on suspicion of committing fraud in connection with a real-estate deal, human rights lawyer Mo Shaoping told AFP, adding that the evidence of fraud was "insufficient".

"He (Liu Hui) should face trial soon, within a month," Mr Mo said, adding that he had been detained after becoming involved in a "civil dispute".

Liu Hui is the brother-in-law of Chinese political activist Liu Xiaobo, who was jailed for 11 years in 2009 for "subversion", after circulating a charter calling for democratic reforms, and who was awarded the Nobel Peace Prize in 2010.

The Nobel winner's wife Liu Xia, who is Liu Hui's sister, has been under house arrest in Beijing since her husband was awarded the prize.

Mr Mo could not confirm whether the charges against Liu Hui were connected with the activities of his brother-in-law, but said that he had been under constant "surveillance by public security units" in recent months.

Liu Hui was first arrested last year, and later released on bail, Mr Mo said.