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PONNAGYUN, Myanmar—Last June, the Myanmar subsidiary of telecom Telenor Group received an urgent government order it was told it must not disclose. Turn off the internet in nine townships.

Hans Martin, a senior executive at the Norwegian company, saw red flags. He said Myanmar’s justification—that people were using the internet to “coordinate illegal activities”—was vague, and no end-date was given. The telecom said it had little legal basis to refuse the order, and complied.

Nearly 250 days later, western Myanmar has become the site of one of the longest internet shutdowns documented anywhere in the world.

From autocratic Iran to democratic India, governments are cutting people off from the global web with growing frequency and little scrutiny. Parts or all of the internet were shut down at least 213 times in 33 countries last year, the most ever recorded, according to Access Now, a nonprofit that advocates for a free internet and has monitored the practice for a decade. The shutdowns were used to stop protests, censor speeches, control elections and silence people, human-rights advocates said.

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Pakistan tailored shutdowns to isolate and control specific neighborhoods, while Iraq automated internet curfews at certain times of the day. Venezuela blocked social media apps, such as Facebook and Twitter. Bangladesh throttled mobile data speeds to 2G levels, making it impossible to share photographs, watch videos or even load most websites.

“What I’m seeing is a definite increase in the shutting down of the internet for political reasons,” said David Kaye, the United Nations’ special rapporteur for the protection of free expression, who monitors rights violations across the globe and reports to the U.N.’s Human Rights Council.

Dozens of interviews with telecom officials, diplomats, researchers and rights advocates revealed how very little stands in the way of governments that want to block the internet, even for long periods.

No global agreements explicitly cover internet freedoms, though the right to information is guaranteed under the Universal Declaration of Human Rights, a nonbinding set of principles adopted by the U.N. Telecom companies, which rely on government licenses and agree to follow a nation’s laws, rarely push back. Those that try to ask questions or negotiate find they don’t have much leverage.

Myanmar’s telecom ministry didn’t respond to requests for comment.

Across the world, hundreds of companies offer access to the internet, including private-sector multinationals and state-owned firms. Their control over who can do what online makes them valuable to governments. The companies can pinpoint user locations, block apps and websites, and turn off access within minutes.

Companies emerging as prominent players in markets across Africa, Asia and the Middle East—including India’s Bharti Airtel Ltd., Malaysia’s Axiata Group Bhd. and Qatar’s Ooredoo QPSC—disclose little information about how they handle government orders or when and why they turn the internet off. The companies didn’t respond to requests for comment.

Only a few telecom firms publish data on the number of government requests they receive to intercept messages, shut down networks, restrict content and share user details. Even those reports leave out orders or actions that authorities want to keep secret.

“We’re often restricted by law to disclose the details or acknowledge any requests received,” said Laura Okkonen, the senior human-rights manager for U.K.-based Vodafone Group PLC. “We have, as a company, tried to be as transparent as legally possible.”

In the U.S., major telecommunications companies such as AT&T Inc. and Verizon Communications Inc. publish reports disclosing the number and nature of demands they receive from government and law-enforcement bodies. These can include subpoenas for subscriber information, court orders for wiretaps, emergency requests for information and in some cases rough estimates of National Security Letters issued by the FBI.

To uncover or confirm shutdowns that aren’t disclosed, some internet monitoring groups rely on diagnostic tools that measure changes in network activity. Access Now and U.K.-based NetBlocks track dips in network data to call attention to disruptions, such as in Venezuela and Iran in recent months.

After Iran ordered a shutdown in November, a research lab in California, the Center for Applied Internet Data Analysis, ran tests measuring connectivity. It produced a detailed sequence of the weeklong blackout, including how devices were severed from the global internet, though users could visit Iranian websites, which are largely government controlled.

The first time it’s known that a government ordered a nationwide internet blackout was Jan. 28, 2011. Internet trackers call it a turning point. The popular revolts of the Arab Spring were spreading to Egypt, and protests against then-President Hosni Mubarak were growing. Twitter, Facebook and messaging apps were being widely used to share information and coordinate protests. The government ordered all internet providers to disconnect, and almost immediately, 80 million people were offline.

After services were out, soldiers armed with machine guns barged into the office of Mobinil—majority owned by French telecom company Orange SA—and demanded that they blast out a text message praising the president’s glory, according to Yves Nissim, a corporate social responsibility officer at Orange. Staff sent out the message, at gunpoint, but insisted that it be attributed to the army.

“This was just unheard of before,” Mr. Nissim said. “We decided after that we couldn’t face this alone.”

Over the next two years, seven multinational telecom companies, including Orange, Telenor and Vodafone, formed a group to compare their experiences and align arguments used to negotiate with authorities. They said they established standards to disclose government requests, and that they have made some orders less severe through negotiations.

But the practice is more widespread than ever. On Nov. 16, Iran switched the entire nation offline as authorities carried out a deadly crackdown on antigovernment protesters. Iraq did the same in October, and again a few weeks later. Sudan did it in June. Zimbabwe in January 2019.

India’s government has faced criticism for blocking the internet in Kashmir after its decision in August to end the region’s partially autonomous status. Officials argue the move is required for public security, which they said trumps the right to internet access. Critics said the shutdown is aimed at blocking protesters.

India’s Supreme Court ruled in January that the blackout was unconstitutional. Authorities have restored limited fixed-line services while leaving mobile data and social media cut off.

“India is a swing state in the future of democratic governance of the internet,” said Adrian Shahbaz, research director for technology and democracy at Freedom House, a U.S.-based human rights group. “When a massive democracy like India resorts to such a blunt tool, it normalizes the approach of shutting down the internet.”

In Myanmar, the internet only became widespread over the past five years, after the country’s telecom sector opened up as part of a transition from military rule toward democracy. Mobile towers sprang up across the countryside, and the price of SIM cards—the chips that connect phones to a mobile network—dropped from about $250 to $1.50 almost overnight.

In rural Ponnagyun, in the western state of Rakhine, residents said the internet’s arrival had just started to transform their impoverished communities. E-commerce and digital services such as money transfers were trickling in, and travel operators and farmers had adopted new ways of working.

San Naing, a 40-year-old rice farmer, said he could communicate with buyers more efficiently, send them photographs and arrange large deliveries. Since the shutdown, he has returned to his old practice of bringing huge hauls of rice to the nearest town by boat, hoping to unload it at the market. “It’s like we suddenly went blind,” he said.

In this part of the country, Myanmar’s military, which has been widely criticized for its violent operations against the country’s many insurgent groups, is fighting a group of ethnic rebels called the Arakan Army. Clashes intensified in early 2019 and surged again in recent weeks.

The shutdown affects areas that are home to both Rakhine Buddhists and a few hundred thousand Rohingya, a persecuted Muslim minority. Myanmar is facing genocide allegations at the U.N.’s top court after military operations in 2017 forced more than 700,000 Rohingya to flee to Bangladesh.

It was after hours on June 20 when the Myanmar subsidiary of Telenor, Norway’s state-owned telecom firm, received the government’s email. It had until 10 p.m. the next day to turn off the internet in nine townships, including Ponnagyun, according to Mr. Martin, Telenor’s chief corporate affairs officer in Myanmar.

The order, parts of which were read to the Journal, cites the country’s telecommunications law, which allows the government to suspend services “when an emergency situation arises.”

The company’s regulatory officer had already begun quiet preparations after a heads-up from a government source a few days earlier, according to the company’s head of technology operations, Abdur Raihan. Over two days, a small team of engineers identified the towers whose antennae transmit signals into the relevant townships. An engineer wrote a piece of code that would instantly disable the antennae, Mr. Raihan said.

Mr. Martin said his first thought on the morning after the order arrived was that obeying it could set a bad precedent, signaling to authorities that they would face little resistance if they tried to do the same elsewhere. The Arakan Army is only one of more than 20 armed groups in Myanmar, which is home to one of the world’s longest and most complex civil wars.

The company’s legal and sustainability officers weighed in with concerns that the order was too open-ended and might disproportionately affect civilians. Telenor representatives communicated with the telecom ministry several times throughout the day, pressing for details on why the shutdown was necessary and how long it would last. They were told the government had nothing to add.

Despite its concerns, Telenor decided to comply because the company’s lawyers found the order to be legal, Mr. Martin said. But it told a top bureaucrat in the telecom ministry, Soe Thein, that the company would alert customers with a text message and a public statement. Mr. Thein was clearly displeased, according to Telenor, but didn’t try to forbid it.

At 10 p.m., service went down. Telenor customers’ mobile phones in the blackout zone lit up with a message saying the government had ordered the disruption, and service would be restored “as soon as possible.”

The government order was also addressed to the country’s three other telecom providers—state-owned Myanmar Posts and Telecommunications, state-controlled MyTel and Qatar-based Ooredoo—who also complied. The companies didn’t respond to requests for comment.

In September, the government lifted restrictions in five townships, while four remained offline. In early February, the government reimposed the blackout in the five townships, citing “security requirements and public interest,” Telenor said.

Locals said that within days of the renewed blackout a major offensive against the rebels was under way in the region. On Feb. 18, the U.N. expressed grave concern over a surge in civilian casualties and urged the government to end the internet shutdown.

Write to Feliz Solomon at feliz.solomon@wsj.com