BEIJING — When visiting friends in China’s capital, environmental activist Wu Lihong must slip away from his rural home before sunrise, before the police officers watching his home awaken. He rides a bus to an adjacent province and jumps aboard a train just minutes before departure to avoid being spotted.

In a neighboring province, veteran dissident Yin Weihong finds himself hauled into a police station merely for keeping in touch with old friends from the 1989 Tiananmen Square pro-democracy movement. While he’s technically a free man, the treatment makes it virtually impossible to keep a job or have a normal home life.

A quarter century after the movement’s suppression, China’s communist authorities oversee a raft of measures for muzzling dissent and preventing protests. They range from the sophisticated — extensive monitoring of online debate and control over media — to the relatively simple — routine harassment of government critics and maintenance of a massive domestic security force.

The system has proven hugely successful: No major opposition movement has gotten even a hint of traction in the 25 years since Tiananmen. President and Communist Party leader Xi Jinping seems intent on ensuring things stay that way.

“It’s extremely bad right now, much worse than in past years,” said Yin, who spent several months in prison for his role as a student leader during the 1989 protests. “There’s less and less space for civil society or, if you’re like me, even to just live your life freely.”

Each year’s anniversary brings a crackdown on dissent, but this year has been especially harsh, say dissidents and human rights groups. Lawyers and others taking part in even minor private commemorations have been detained. Outspoken relatives of those killed in the crackdown have been forced out of Beijing.

Journalists, including those in the foreign media, have been issued stern orders not to report on unspecified sensitive topics around the June 4 anniversary, with warnings of dire consequences.

“We are seeing a crackdown very large in scope,” said William Nee, Amnesty International’s Hong Kong-based China researcher. “What we have seen thus far under the Xi Jinping government hasn’t been very good.”

Caught unaware and unprepared by the Tiananmen protests, China now anticipates, detects and chokes off political and social activism before it can challenge authorities. Despite a huge rise in prosperity and vast social changes, political activism and organization outside the control of the ruling Communist Party is strictly verboten.

“The authorities are very careful to nip any potential dissent in the bud at the local level, the focus being on ensuring they can’t link up and become a nationwide movement,” said Human Rights Watch Asia researcher Maya Wang.

Yin said China’s rights conditions have deteriorated since party stalwart Xi Jinping’s appointment as general secretary in late 2012. While going after corrupt officials, Xi has demanded strict ideological orthodoxy and pushed a campaign to denigrate liberal values such as Western-style constitutional democracy and the independence of the media.

Government critics and public intellectuals face ever-more-intrusive harassment, Yin said. Liu Xia, the wife of imprisoned Nobel Peace Prize winner Liu Xiaobo, is under house arrest and constant supervision. An unknown number of others can leave home or work only with permission.

Some veteran activists say the room for independent organization is tighter than it was in 1989. A limited number of nominally non-governmental organizations are permitted, but they operate only at the pleasure of the authorities and must confine themselves to non-political issues such as environmentalism, child welfare and workers rights.

“It’s OK to hold lectures and conferences, at least in principle, but you can’t really conduct research and seriously delve into the topics,” said Wu, an environmental activist from the eastern city of Wuxi who has endured more than a decade of harassment, including a three-year prison sentence on fraud charges he says were trumped up.

Some degree of labor activism has been permitted, especially in the southern industrial heartland of Guangdong province, but the only legal unions remain under tight government control and strikes are extremely rare.

Independent workers’ rights activists are under constant scrutiny. Anita Chan, a China labor expert at Australia National University, said police are more frequently calling the activists in to “drink tea” — a form of low-level intimidation.

And while religious activity is permitted under the auspices of party-controlled bodies, crackdowns have escalated against independent groups such as Protestant “house churches.” In Zhejiang province alone, 64 churches were demolished, had their crosses removed or were threatened, according to Bob Fu, a former dissident and underground church pastor now based in Texas.

Meanwhile, the state has developed increasingly sophisticated mechanisms of surveillance and censorship, taking advantage of technological improvements and a huge boost in domestic security spending. An army of young, computer-savvy censors checks social media and websites and removes content on sensitive topics.

Users of social media such as the hugely popular microblogging and instant messaging applications Weibo and QQ must be registered and identified.

Many foreign websites are blocked, including news outlets and Twitter, Facebook and YouTube. Those who care to make the effort can find technological workarounds, such as virtual private networks, but most Chinese appear content with the Internet that the government allows.

The government has come down hard on some outspoken online opinion leaders, detaining many for so-called rumor mongering, including a well-known liberal commentator, Chinese-American investor Charles Xue.

Wang, of Human Rights Watch, said the government is trying to compel people to censor themselves.

“It’s so that when people go about their business, they already consider the potential risks and make sure they don’t even get close to the red lines,” Wang said.

Another standard control method is to restrict travel. Many critics of the government, including Wu and Yin, have been denied passports — both as a punitive measure and a means to keep them from addressing foreign audiences about China’s problems.

And while Wu can use some ingenuity to visit his friends in Beijing, he said, “As soon as they find I’m gone, they send officers to bring me back. You try to adapt, but it takes a real toll on your family and on you psychologically.”

Shortly after The Associated Press interviewed him, Wu was taken from a friend’s home and interrogated for 24 hours straight.

Despite these efforts, China sees what many of what it calls “mass incidents” threatening social stability. One Chinese sociologist, Sun Liping, has estimated there are about 180,000 per year, ranging from organized marches to spontaneous protests and even violence sparked by anger over working conditions, corruption, environmental degradation and ethnic unrest.

A premium is placed on quickly containing and dissolving such incidents, unlike in 1989, when protests were allowed to build up over more than a month.

The government also has focused heavily on avoiding military force such as the tanks and troops that tore their way through citizen barricades to the heart of the protests in Tiananmen Square, leaving hundreds, possibly thousands dead.

Instead, the government has vastly expanded its domestic security apparatus. Much of the effort has gone into improved training and equipment for the 1.5 million-member paramilitary People’s Armed Police, the Chinese interior security force. Grassroots-level officials and public security department heads have undergone training in responding to unrest.

Meanwhile, the party has tackled many of the major contributing causes of the 1989 protests, devoting funds and attention to fighting corruption, boosting employment and housing and even holding down pork prices. That has eliminated many sources of discontent, though many Chinese remain deeply cynical about corruption among the newly rich and political elites.

“They realize that economic growth is not enough, so the whole strategy is to avoid cases of large-scale unrest through an entire social security package,” Joseph Cheng said.