China has accused U.S. Secretary of State Mike Pompeo of smearing its domestic and foreign policies in a critical statement he issued on the 30th anniversary of the crackdown on the 1989 Tiananmen Square protests.

A Chinese spokesperson said in a post Tuesday on the website of the Chinese embassy in Washington, D.C., that Pompeo’s statement “grossly intervenes” in China’s internal affairs and is “an affront to the Chinese people and a serious violation of international law.”

Pompeo’s statement saluted the protesters and urged the Chinese government to make a full public accounting of those killed in the crackdown. It added that America’s hopes that China would become a more open and tolerant society have been dashed.

In Beijing on Tuesday, Chinese authorities stepped up security around the square.

Extra checkpoints and street closures greeted tourists who showed up to watch the daily flag-raising ceremony. An honour guard marched across a barricaded street and raised the Chinese flag.

Foreign journalists were not allowed onto the square to record events.

Hundreds, if not thousands of people are believed to have been killed in 1989 when the government sent in the military to clear Tiananmen Square of protesters in an operation that began the night of June 3 and ended the following morning.

Any commemoration of the event is not allowed in China.