BEIJING — With the 25th anniversary of the Tiananmen Square crackdown less than a month away, China has launched a broad effort to muzzle and detain citizens who are attempting to remember the victims.

On Tuesday, authorities detained human rights lawyer Pu Zhiqiang and at least five other activists who had attended a Tiananmen seminar in Beijing three days earlier.

Then, on Thursday, state media reported that authorities had “criminally detained” prominent journalist Gao Ju – once jailed for her writings during the 1989 protests – and accused her of sharing a government document with a foreign website.

The detentions, coupled with other recent actions against activists associated with the Tiananmen protests, are a further demonstration that Chinese President Xi Jinping plans to take a hard line on free speech, even as he preaches the need to “open up” and reform China’s economy.

“Since Xi Jinping took power, things have intensified significantly,” said Yaxue Cao, a Washington-based human rights activist who runs the China Change website.

Cao says the stepped-up police action is related to the significance of the 25-year anniversary, as well as internal worries about maintaining control. “This year, the Chinese Communist Party feels particularly vulnerable,” said Cao, noting that there have been recent protests in Taiwan and Hong Kong against Beijing’s influence.

For nearly a quarter-century, China’s communist party has effectively banned any public mention of the Tiananmen protests, which drew thousands to Beijing’s central square for weeks, and the military’s response, in which hundreds of people died. When people type “June 4” into Baidu, China’s main search engine, they get a message in Chinese that says: “According to policies from relevant laws and regulations, part of the search result cannot be displayed.”

William Nee, a Hong Kong-based China researcher for Amnesty International, said the government’s recent actions were “an attempt at forced amnesia.” He noted that President Xi delivered a speech in January in which he said Chinese leaders needed to balance social stability with the demand for justice. “But their default when they get into trouble is to fall into a ‘stability above all’ mindset,” he said.

The arrest of Pu Zhiqiang stunned many in Beijing. Pu is a well-known lawyer, having represented artist Ai Weiwei and other dissidents. At one time he seemed in the good graces of the government, quoted prominently in state media as part of a successful campaign to end forced-labor camps.

Pu gathered at a private home with a dozen other Beijing intellectuals May 3. The group urged a probe of the 1989 military assault on the pro-democracy protesters. As they did five years ago, those in attendance posed for a photo that was posted on social media.

Three days later, authorities detained Pu for “picking quarrels and causing trouble.” At least four others at the meeting also were detained, according to media reports and human rights groups.

Hu Jia, a pro-democracy activist who has effectively been under house arrest in Beijing for a decade, told McClatchy he was surprised that authorities “cracked down so fast and so severely.” There were no detentions of Pu and others when the group met openly five years ago. “The punishment is drastically different this time,” Hu said in a telephone interview.

On Wednesday, U.S. State Department spokesman Jen Psaki urged China to release Pu and others and guarantee their protections and freedoms.