The United States and Taiwan have pressed China to release dissidents and fully address the bloody crackdown on pro-democracy demonstrations around Tiananmen Square 22 years ago.

The U.S. State Department issued its statement Friday, on the eve of the anniversary of the June 4, 1989 crackdown — when China's government sent tanks and troops into Tiananmen Square to crush weeks of student and worker protests. Hundreds, perhaps thousands, of people died.

The State Department called for the fullest possible public accounting of those killed, detained or missing, and a halt to ongoing harassment of those who participated in the demonstrations and the families of victims.

Taiwan President Ma Ying-jeou said China should follow Taipei's example and reform politically.

Thousands of Chinese and foreign tourists packed Tiananmen Square Saturday, where security was particularly tight amid a harsh, four-month crackdown on activists, lawyers and bloggers.

The group Chinese Human Rights Defenders said Saturday that security officers took former government official Bao Tong to an unknown location this week. And, the Information Center for Human Rights and Democracy said liberal intellectual Chen Ziming and many others have been placed under house arrest.

Beijing has never admitted responsibility for the Tiananmen killings. The subject is particularly sensitive this year, after online calls for an Arab-style “jasmine revolution in China.”