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.

Activists hold vigil in Hong Kong

Pro-democracy activists in Hong Kong held a candlelight vigil commemorating the anniversary, underscoring concern for Chinese human rights in the semi-autonomous territory even as its own civil liberties are under threat.

Hong Kong is the only region under Beijing's jurisdiction that holds significant public commemorations of the 1989 crackdown and memorials for its victims. Hong Kong has a degree of freedom not seen on the mainland as a legacy of British rule that ended in 1997.

The annual evening event at Hong Kong's Victoria Park near the bustling Causeway Bay shopping district was expected to attract tens of thousands of participants.

This year's vigil featured a replica of the "Goddess of Democracy," a plaster sculpture of a female figure holding a torch that was displayed in Tiananmen Square in the days leading up to the crackdown.

"That statue was crushed by tanks at the June 4 crackdown, the June 4 massacre. So we are rebuilding this here ... to symbolize that we are still continuing to fight for democracy, and continue on the spirit of the '89 democratic protests," said Chow Hang Tung, vice chair of the Hong Kong Alliance in Support of Patriotic Democratic Movements in China, which organized the annual vigil.

A replica of the "Goddess of Democracy," a plaster sculpture of a female figure holding a torch that was displayed in Tiananmen Square in the days leading up to the crackdown, stands in Hong Kong as part of the 30th anniversary commemoration. (Philip Fong/AFP/Getty Images)

Recent years have witnessed a generational divide about how best to memorialize the crackdown, and since 2015, Hong Kong university students have arranged their own commemorations separate from the main candlelight vigil.

"People who attend the vigil consider themselves Chinese. We disagree with this identity," said Jordan Pang, acting chair of the Hong Kong University Students' Union's current affairs committee.

"I think the young generation and most students consider themselves Hong Kongers. If we need to commemorate, we do not want to use [the vigil] to commemorate," Pang said.

Despite its pro-democracy theme, young Hong Kongers see the vigil as promoting Chinese nationalism, said Samson Yuen, a professor of political science at Hong Kong's Lingnan University.

"They argue that Hong Kong needs to determine its own future. Hong Kong may need to seek independence from China and they believe that June 4 is a battleground," Yuen said.