BEIJING (AP) -- Chinese police detained the wife of the co-founder of a Mongolian separatist movement and raided the family bookstore just days before the activist is to be released from 15 years in prison, his son said Saturday.

Unrest among ethnic Mongolians in China is not as well known as that among ethnic Tibetans and Uighurs, but the scheduled release next Thursday of Hada, who like many ethnic Mongolians uses just one name, has brought a round of complaints about police harassment.

Hada helped found the Southern Mongolian Democratic Alliance, seeking to establish an independent nation in China's Inner Mongolia region.

Hada's bookstore in the Inner Mongolia capital of Hohhot became the center of the movement, and more than 200 people demonstrated in front of the store on Dec. 30, 1995, singing and holding up images of Genghis Khan, the legendary 13th-century Mongolian conqueror.

Hada was sentenced to prison the next year after being accused of separatism and spying.

In the month leading up to Hada's scheduled release, his family has said they have not been able to contact him as before.

Just before noon Friday, more than 10 police officers raided the bookstore, confiscating the account book and computer, Hada's son Wei Lesi told The Associated Press by telephone Saturday.

He said police also detained Hada's wife, Xinna, who has been outspoken about her husband's treatment.

"I was surprised and very angry," Wei said.

Xinna has also spoken publicly in support of Charter 08, a statement co-authored by imprisoned Nobel Peace Prize winner Liu Xiaobo demanding more freedoms in China. Dozens of activists in China have reported greater police pressure in the weeks leading up to the Nobel ceremony for Liu next Friday.

Police in Hohhot's Saihan district, which carried out the raid, did not comment.

"People often hear how miserable people were during the Cultural Revolution and how bloody it was at Tiananmen Square, but the things that happened yesterday make me feel that after 30 years of reform and opening up, law and human rights in today's China are still wantonly trampled by those barbarian and lawless law enforcers," Wei said in a letter addressed to Zhou Yongkang, secretary of the ruling Communist Party's political and legislative affairs committee. Wei sent a copy of the letter to the AP.

"I hope you can bring these evil law enforcers to justice and let us enjoy a hard-won family reunion after 15 years," Wei's letter said.

The U.S.-based Southern Mongolian Human Rights Information Center has said another Mongolian activist, writer Govruud Huuchinhuu, was detained last month and put under house arrest for trying to organize a rally to welcome Hada's release.