BEIJING — A detained Chinese legal activist delivered a bold message from inside a Beijing jail, urging citizens to unite in pursuing democratic freedoms in a video posted online Thursday that's sure to anger the authorities.

In the video, civil rights campaigner Xu Zhiyong is seen handcuffed and wearing what appears to be an orange detainee vest over a dark T-shirt, seated at a table behind bars.

"No matter how utterly defeated or absurd this society is," Xu said in the video, "this country needs brave citizens who can stand up and hold fast to their convictions, who can take their rights, responsibilities and their dreams seriously."

Xu's supporter and friend, Wang Gongquan, confirmed by phone that he had obtained the video and posted it on his microblogs.

Wang said one of Xu's lawyers, Zhang Qingfang, shot the video on Aug. 1.

Beijing police did not immediately respond to a fax seeking comment on the video.

Xu is a moderate but outspoken voice in China's beleaguered rights movement, campaigning for issues that include equal rights to education, and for officials to declare their assets.

Not one to call for the overthrow of the Communist Party, Xu has preferred to advocate that the government live up to its promises to protect the rights of the people enshrined in the country's oft-ignored constitution.

He most recently was detained in mid-July, sparking an outcry among rights activists and academics in China and criticism from the U.S. State Department.

Xu is accused of "gathering people to disturb order in a public place," a charge that has been increasingly used to punish people who speak out against abuses.

"The authorities' detention of Xu Zhiyong is totally unacceptable and the charge is completely without basis," Teng Biao, a rights lawyer and close friend, said Thursday.

In 2009, Xu was detained and formally arrested on suspicion of evading taxes — allegations seen as a bid to stop him in his work in a legal aid organization that represented politically sensitive cases. He was released after spending about a month in jail, though hefty fines were levied on the group by the Beijing tax bureau.

In recent years, Xu has advocated a movement urging the Chinese public to build a stronger civil society that is fair and just. Activists are frequently harassed, making it unclear how large the nascent movement's following might be.

Xu's latest detention indicates how unsettled the authorities are by even the smallest hint of organized civil activity and his ability to rally support around a message.

"Let us unite and work together," Xu said in the video, urging people to take their rights and identities as citizens seriously and work to promote democracy and the rule of law.