Updated

Beijing police have detained a Chinese news assistant for a Japanese newspaper, her family said Wednesday, in the latest in a string of detentions ahead of the 25th anniversary of the 1989 crackdown on pro-democracy protests in Tiananmen Square.

The newspaper, Nihon Keizai Shimbun, said it was looking into the case but declined to provide further details.

The family of Xin Jian, an employee in the newspaper's bureau in the southwestern city of Chongqing, said she was detained on suspicion of picking quarrels and provoking troubles. There was no immediate explanation of the allegations.

Every year, the government attempts to prevent any commemorations or public discussions of the anniversary of the June 4, 1989, crackdown, but activists say this year has been one of the most severe clampdowns. Such restrictions usually are put in place a few days before the anniversary, but this year many dissidents say they have been placed under house arrest months ahead of the date and have been warned against talking to the media.

"The response by the Chinese authorities to the 25th anniversary has been harsher than in previous years, as they persist with trying to wipe the events of 4 June from memory," Salil Shetty, secretary general of Amnesty International, said in a statement.

Those detained include a human rights lawyer, Pu Zhiqiang, and a prominent journalist, Gao Yu. Ding Zilin, a founder of the Tiananmen Mothers, which represents families of those killed in the military attack on protesters, has been placed under house arrest.

Xin was taken away from her Chongqing home on May 13 after police detained Pu and four others for attending a May 3 commemoration of the crackdown.

The Nihon Keizai Shimbun said police initially told Xin's family that they wanted cooperation in Pu's case. Xin had assisted reporters in interviewing Pu, best known for his successful lobbying for the closure of Chinese labor camps. Police had used the camps to lock up people for up to four years without legal process.

A woman who answered the phone at Xin's house and identified herself as the news assistant's mother confirmed that she had been detained on the charges. She declined to provide further information, saying the phone line was tapped.

"We believe she is innocent," she said.

Beijing police did not immediately respond to a request for information.

Chinese authorities have warned foreign journalists of "extreme consequences" if they report on sensitive issues ahead of the anniversary.

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Associated Press writer Mari Yamaguchi in Tokyo contributed to this report.