China had tightened its security for the Tiananmen Square protest's 25^th anniversary, but exiled former rally leader Zhou Fengsuo managed to slip back into China undetected.

Zhou was included in the 1989 list of the 21 most-wanted students by the Chinese government. Now 47, the former Beijing Students Autonomous Federation leader had spent two days visiting Tiananmen Square and some friends in a detention center before getting caught by authorities, according to The New York Times.

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The authorities interrogated Zhou for 18 hours before putting him on a flight back to the US, where he had spent two decades of his life since he left his mother country and is now an American citizen.

Except for one, none of the 21 students on the most-wanted list who were exiled have been allowed to return to China. Most dissidents who go to another country cannot return home, even to attend the funeral of a parent.

Fearing that citizens would try to celebrate the 25^th anniversary of the Tiananmen Square protest, the Chinese government has detained or exiled many dissidents. Zhou recalled that he had expected his application for a 72-hour visa to be denied, but he was surprised when he made it past Beijing International Airport.

Zhou's first stop in Beijing was the police detention center where some of his old friends and several other activists have been held for attending a private meeting last month to tackle the Tiananmen crackdown. The former protest leader said the police did not allow him to send cash to the detainees, but they did not appear to know his name.

The following night, a friend toured him around the city to revisit some historic protest landmarks including Muxidi, Jianguomen, and Tiananmen Square. Twenty minutes after returning to his hotel, police officers showed up and he was picked up for interrogation. Zhou said the interrogators were polite and some were even empathic.

Zhou was studying physics at Tsinghua University when his sister turned him in to the police and he was jailed for a year. He went to the US in 1995 and took up a business course in the University of Chicago. He is the founder of Humanitarian China, an organization that serves as an advocate for Chinese political prisoners.

This was Zhou's third trip back home, with the two other secret trips taken in 2007 and 2010. He decided to travel to China this week to "show some solidarity" with his friend Pu Zhiqiang, who was also detained, and those who were killed in the Tiananmen incident 25 years ago.

Under the terms of his negotiations with the Chinese authorities, Zhou was assured that they would leave Pu alone. Zhou said they seem to have stayed true to their agreement.

TagsTiananmen, Square, Protest, 25th, anniversary, exile, Zhou Fengsuo