· Campaigner had been told not to talk to foreign press · Fear of detention amid pre-Olympic crackdown

A prominent human rights lawyer has gone missing, presumed detained by the authorities, amid a crackdown on dissent ahead of the Beijing Olympics.

Teng Biao - who has defended Aids activists, Falun Gong practitioners and farmers fighting for their land - was last seen on Thursday, being bundled into a black car outside his home in Beijing.

He had recently been warned by police that he would be detained unless he stopped talking to the foreign media and writing about human rights abuses in the runup to the Olympics.

Shortly before he went missing, Teng told the Guardian that his passport had been seized, his phone bugged and his emails checked by the authorities.

He was warned that he also faced the sack from his job as a lecturer at the China University of Political Science and Law and risked detention.

"They told me I cannot accept any interview related to human rights and the Olympics. I said I cannot make such a promise. I have a right to speak," he said last week. "I'm not sure if they will arrest me tomorrow. But I feel no fear."

His wife, Wang Ling, said Teng left home at 8.25pm, saying he would be back in 20 minutes. About half an hour later, she heard shouting downstairs. Two witnesses told her that a man had been pulled out of the family's car and taken away.

"It is strange because my husband is a very nice man who had no personal conflicts with anyone," she said. "I don't understand why this happened."

Sources who met Teng this week said the lawyer looked downcast and under pressure because police had threatened to charge him with inciting subversion of state power, which carries a sentence of several years in prison.

This accusation is often levelled at dissidents. Last month, Hu Jia - a friend of Teng and a prominent civic rights and Aids campaigner - was arrested and is likely to face a similar charge.

Teng and Hu co-wrote an open letter last September that highlighted China's failure to live up to its Olympic promise to improve human rights before the games, which will take place this August.

"When you come to the Olympic games in Beijing, you will see skyscrapers, spacious streets, modern stadiums and enthusiastic people. You will see the truth, but not the whole truth, just as you see only the tip of an iceberg," the pair wrote. "You may not know that the flowers, smiles, harmony and prosperity are built on a base of grievances, tears, imprisonment, torture and blood."

At least two other activists - Liu Jie and Yang Chunlin - have been put in prison or re-education camps after linking the Olympics to human rights campaigns or petitions against land seizures.

International human rights groups said they were deeply concerned about Teng.

"The detention of a member of the Beijing bar association signals an escalation in the repression against dissent ahead of the games," said Nicholas Bequelin, of Human Rights Watch. "We urge the International Olympic Committee to end its silence about the suppression of Olympic critics by the Chinese government."

Teng was aware of the political sensitivity of the Olympics, which he believed was the reason why Hu was arrested this year. "It is very, very dangerous for Chinese people to hold any kind of protest before the Olympics," he said.