BEIJING -- The Chinese capital was put on high alert Tuesday, the 30th anniversary of a military crackdown on pro-democracy demonstrators in Tiananmen Square that left many dead.

Large numbers of security cameras and police officers were deployed around the square and other locations.

Under President Xi Jinping, the government has raised alert levels compared to previous years around this time, apparently out of fear that a new pro-democracy movement could take shape.

In the morning, a number of police vehicles entered the square, and many officers were seen standing by inside a large bus marked "Public Security."

Roads around the square were congested due to traffic restrictions. Police were seen questioning pedestrians.

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Although tourists were being allowed to enter the square after showing their identification and having their bags checked, journalists were banned from entering.

China censors all reports of the crackdown. Chinese people cannot talk about the crackdown publicly out of fear doing so could put them in serious jeopardy. Major newspapers carried no articles about the anniversary in their Tuesday editions.

Officially, Tiananmen was "political turmoil that occurred in the late 1980s," Geng Shuang, deputy spokesman for the Chinese Ministry of Foreign Affairs, said in response to questions during Monday's news conference. The exchanges between Geng and reporters have not been posted on the ministry's website.