An outspoken Beijing lawyer has been arrested for tax evasion nearly three weeks after he was detained, his lawyer said Monday.

Xu Zhiyong, co-founder of Gongmeng, a legal assistance group, was taken from his home by security officers at dawn on July 29, according to a statement from Gongmeng.

Zhou Ze, Xu's lawyer, told China Daily Tuesday that Beijing prosecutors had approved a police application to arrest Xu for tax evasion.

Beijing municipal authorities ordered the closure of Gongmeng last month for not being "registered properly". Beijing tax authorities also sent a formal notice to the center last month, imposing a fine of 1.4 million yuan ($207,000) for evading taxes on funds received from overseas.

The notice of his arrest has been sent to Beijing University of Posts and Telecommunications, where Xu works as a professor.

An officer with the university's security department who declined to be named due to the sensitivity of the issue confirmed to China Daily that the school had received the notice, but would not give further details.

Press officers with the Beijing public security bureau and procuratorate said they have no information about Xu's arrest.

The arrest brings Xu's case closer to a possible trial, although officials have not made a firm decision to prosecute. If tried and found guilty, Xu faces a maximum penalty of seven years in jail, according to the Criminal Law.

But Zhou said he considers the charge improper as only intentional tax evasion or the refusal to pay taxes despite of government notification could result in a criminal punishment.

"Neither of these two conditions apply to Xu's case. He has never been informed of failing to pay tax before," Zhou said.

Xu is currently being kept at the Beijing detention house, Zhou said.

"I paid a visit to him last Friday and he looked fine," he said.

Zhou said that there is no need for others to associate the charge with speculation that the government is cracking down on Gongmeng.

"We will try to defend him for the charge of tax evasion and I hope people won't associate too much with it."

Xu, in his late 30s, gained national attention in 2003 when he took up the case of Sun Zhigang, a college graduate who died after being beaten in a penitentiary hospital in the southern province of Guangdong.

The case helped to bring about the abolition of such penitentiary hospitals used to hold migrants accused of not having the right documents.

The combination of legal casework and public advocacy used by Xu and his colleagues set an example for many subsequent campaigns.

In 2005, Xu registered the Gongmeng group. With other scholars and lawyers, Xu has been providing legal help to the country's disadvantaged groups, including some of the parents of children who fell ill after drinking contaminated milk powder last year.

Information about Xu has been blocked on the internet Tuesday as the search for "Xu Zhiyong (Chinese characters)"on Google.cn and Baidu, two major search engines, generated: "Your search results don't conform to related laws and policy".