NEW DELHI — The pardon was swift and stunning, overturning the landmark conviction of an army sergeant for massacring civilians during Sri Lanka’s civil war.

Human rights groups decried the move, but there were no protests. Nor were there any in-person appeals. Even a legal challenge was impossible: With all of Sri Lanka under a strict nationwide lockdown, the courts, too, were closed.

The decision in March by Sri Lanka’s newly elected president is part of a broader, disturbing trend in which governments around the world have punished opponents, rewarded friends and stifled dissent amid the global pandemic. The overwhelming nature of the fight against the disease combined with physical restrictions on citizens has meant that such actions incite less opposition at home and abroad than in the past.

In Bolivia, the government has arrested dozens of opponents under a new decree passed last month. In India, authorities have pursued activists and journalists using a sweeping anti-terrorism statute. In Cambodia, at least 30 people — many of them opposition supporters — have been arrested ostensibly for spreading misinformation during the pandemic. Several governments have passed laws whose stated goal is to fight the coronavirus but that opponents say provide tools to crack down on critical voices and the media.

While emergency measures may be necessary to combat the spread of the virus, some governments “appear to be using COVID-19 as a cover for human rights violations, further restricting fundamental freedoms and civic space, and undermining the rule of law,” Michelle Bachelet, the U.N. high commissioner for human rights, said in a statement this week.

She called such cases “deeply worrying.”

In Sri Lanka, President Gotabaya Rajapaksa announced the pardon of former army sergeant Sunil Rathnayaka six days after the imposition of a nationwide curfew. Rathnayaka was convicted of murdering eight civilians, including three children, in 2000. The case against Rathnayaka took more than a decade, and his conviction was upheld last year by the country’s top court.

One striking example of a crackdown during the pandemic comes from Bolivia. Before the outbreak, the right-wing government led by interim president Jeanine Áñez presided over the detention of hundreds of opponents, the muzzling of journalists and a “national pacification” campaign that left at least 31 people dead, according to the national ombudsman and human rights groups.

Then, in March, Añez’s outspoken interior minister, Arturo Murillo, unveiled what he called a new “cyberpatrol” — to be run by the armed forces, police and his own staff — with the aim of identifying and prosecuting those deemed to be spreading “misinformation” during the coronavirus outbreak. A subsequent presidential decree stated that violators could be charged with “a crime against public health” and face up to 10 years in prison.

On April 15, the Añez government shocked observers by announcing that 67 “political actors” already had been charged with violating the new decree — and that 37 of them had been “quickly convicted.”

“The government of Bolivia is one of the more crystal-clear cases of a government taking full advantage of this health crisis, this global pandemic, to go after opposition leaders and restrict fundamental freedoms,” said José Miguel Vivanco, Americas director at Human Rights Watch.

Luis Arce, Añez’s principal opponent in the upcoming presidential election, said the recent convictions are especially troubling. “There is no transparency about who they are, what crimes they supposedly committed, or if they are being defended,” he said in a telephone interview. A spokesman for the Añez government did not respond to a request for comment.

In India, the government has moved forward with the controversial prosecution of a well-known academic and critic of Prime Minister Narendra Modi. Anand Teltumbde, a scholar of India’s caste system, was arrested and jailed in April, something he had feared for more than a year. Teltumbde, 70, was charged under an anti-terrorism statute over alleged links to Marxist extremists. Experts and a Supreme Court justice have questioned the validity of the evidence in the probe.

On the eve of his arrest, Teltumbde wrote an open letter calling the case against him a “clumsy and criminal fabrication” and an attempt to strip Indians of their basic rights. “I earnestly hope that you will speak out before your turn comes,” he wrote.

Lawyers for Teltumbde and Gautam Navlakha, a 68-year-old activist also facing arrest, argued before the Supreme Court that sending two senior citizens to prison during the pandemic was “virtually a death sentence.” The court ordered them to surrender within a week.

Teltumbde suffers from asthma and severe inflammation of the spine, said his wife, Rama. She questioned why the government was jailing activists at the same time it is trying to decongest prisons because of the coronavirus. “We only wanted time,” she said. “Are they so dangerous?”

Teltumbde was “duly arrested” after exhausting his legal options, said an official at India’s National Investigation Agency who spoke on the condition of anonymity because the probe is ongoing.

As coronavirus cases rise during an unprecedented nationwide lockdown, Indian authorities have also pursued students and journalists using the same anti-terrorism law, which allows detentions without charges for months.

Two graduate students at Delhi’s Jamia Millia Islamia University — one of whom is pregnant — were arrested last month under the anti-terrorism statute after they helped organize protests against a controversial citizenship law. Authorities accuse them of instigating deadly riots in February. By contrast, a ruling-party politician whose actions helped trigger the violence has faced no charges.

Two journalists in the disputed region of Kashmir were informed that they, too, were being investigated under the same anti-terrorism law. A third Kashmiri journalist, Peerzada Ashiq of the Hindu newspaper, was slapped with a police complaint after he inadvertently included an error in a story.

“They chose a pandemic to go after journalists knowing the entire world is busy dealing with the coronavirus,” said Ashiq. A senior police official in Kashmir, Vijay Kumar, said that the authorities had only investigated journalists who “instigate” violence.

The lockdown appears to have emboldened the authorities to intimidate journalists. Last month, police officers drove hundreds of miles to serve a summons on Siddharth Varadarajan, founding editor of the Wire, an online media outlet that regularly publishes articles critical of the government.

A report on the website had briefly misattributed a quote to the leader of India’s largest state, while also noting that the politician had violated the nationwide lockdown. The complaint accused Varadarajan of crimes including disobeying a public official, transmitting obscene material and flouting India’s epidemic disease act.

“The current offensive against media freedom is especially dangerous as you have a lockdown, so the public depends even more on the media being its eyes and ears,” Varadarajan said. “To straitjacket the media means you’re trying to put a veil on all government functioning.”

Elsewhere, activists fear that the emergency measures passed to combat the virus will serve as pretexts to crack down on opponents and the media. In the Philippines, thousands have already been arrested for violating lockdown measures and President Rodrigo Duterte has threatened to impose martial law. The government passed new legislation in late March to help fight the pandemic. Two journalists have already been charged under the law’s provision against “false information” and now face prison time, according to the advocacy group Reporters Without Borders.

Cambodia, too, passed an emergency law in April that granted its authoritarian leader Hun Sen wide-ranging powers and allows the government to restrict civil and political liberties. Human rights groups have called it a cynical power grab at a time when the opposition in Cambodia is all but neutralized, with key political opponents either in jail or in exile.

The pandemic is “being used as an excuse by governments to tighten their grip on people that they’re uncomfortable with,” said Biraj Patnaik, the South Asia director for Amnesty International. Police are able to make arrests without drawing as much attention, he said, while lockdowns mean it is difficult or impossible for activists to research abuses in person. Judges, meanwhile, are showing deference to the authorities.

“The metaphor of a war, unfortunately, has overtaken the world,” Patnaik said. “There is a feeling that governments need a freer hand because we are fighting a war of some kind.”

Faiola reported from Miami. Shams Irfan in Srinagar, India; Regine Cabato in Manila; and Shibani Mahtani in Hong Kong contributed to this report.