BEIJING  One of the principal student leaders of the 1989 pro-democracy movement flew Wednesday from Taiwan to the Chinese territory of Macao, saying he wanted to surrender to Chinese authorities after two decades in exile.

The former student leader, Wu’er Kaixi, was detained by immigration authorities at the Macao airport on the evening before the 20th anniversary of a bloody military crackdown in Beijing. He told several news agencies that he would return to Taiwan only if he were deported.

“His action is kind of an expression of anger and protest,” said Wang Dan, another former student leader, who is now in the United States.

“Maybe this is his only way to return to China. For all of us, this is the only way.”

In a statement, Mr. Wu’er said his effort to turn himself in was “in no way whatsoever an acknowledgment of guilt in the eyes of the law.”