Updated

A former soldier who took part in the 1989 crackdown on pro-democracy protests in Tiananmen Square and called for a reassessment of the bloodshed was detained Friday, a human rights watchdog said, an indication of the government's nervousness as the event's 20th anniversary approaches.

Zhang Shijun, 40, was taken away three days after giving an interview to The Associated Press. Last week, he published an open letter on the Internet addressed to Communist Party leader Hu Jintao, calling on the party and government to reconsider its condemnation of the student-led protests.

The group Civil Rights and Livelihood Watch said Zhang was taken from his home in the northern Chinese city of Tengzhou about 2 a.m. Friday. The mainland-based group cited a member of Zhang's family who was not identified.

Reached twice by cell phone Friday afternoon, Zhang said he was not at home but declined to give details about his whereabouts. He said he was in touch with local government officials, and that it was "not convenient to talk." Calls to his phone Friday night could not be connected.

Zhang is one of a very small number of soldiers to come forward with their tales and attack the government's refusal to offer a full accounting of the Tiananmen crackdown. Hundreds, possibly thousands, of people are believed to have been killed when troops stormed into the center of Beijing on orders from top party leaders to break up the protests.

Zhang is one of the few to publicly voice regret for the crackdown.

"I feel like my spirit is stuck there on the night of June 3," he said this week, referring to the date in 1989 when the final assault began.

In the 20 years since, China has never offered a full accounting of the crackdown, which government leaders refer to as a "political disturbance." An official silence has been maintained around the incident, with nothing written in school textbooks and public discussion virtually taboo.

Zhang's unit was ordered on June 3, 1989 to drive through the square and get it cleared. He and his comrades were attacked by bricks and rocks, as well as bullets fired by unknown shooters from upper stories of apartment buildings as they moved toward the center of Beijing.

Zhang was unharmed in the final assault and said he knew of no deaths caused by the troops in his unit — a claim impossible to disprove as long as official files on the events remain closed. Most of the post-crackdown reports pinned the civilian deaths on two other units.

Afterward, Zhang said he asked for and eventually obtained an early discharge, never having expected to be sent to fight ordinary Chinese citizens. After returning to Tengzhou he began a discussion group promoting market economics and politics, but was arrested on March 14, 1992 and sentenced to three years in a labor camp for political crimes.

The Chinese leadership is on the alert for such testimonials ahead of this year's 20th anniversary of the crackdown and renewed calls for political liberalization.

Zhang was called into his local police station on Wednesday, a day after the interview, and ordered to avoid contact with foreign media.

A woman who answered the phone at Zhang's home Friday said she was his wife, but that she had not heard from or seen him.