Sri Lankan authorities instituted social media restrictions after several deadly bombings on Sunday — a tactic that experts said is increasingly common around the world: the government-imposed internet shutdown.

From Ethiopia and Venezuela to India and Iraq, authorities are halting the flow of online information in greater numbers amid political turmoil, large-scale protests and other events, said Jan Rydzak, a research scholar at Stanford University's Global Digital Policy Incubator.

Since 2011, Rydzak has documented 400 to 450 cases of internet blackouts, he said. About 150 of those shutdowns occurred last year, many of them in India, he said.

Governments use "a panorama of strategies to control information — this is just one of the most flagrant manifestations of that," Rydzak said.

People living near St. Anthony's Shrine run for safety after police found explosive devices in parked vehicles, which later exploded in Colombo, Sri Lanka, on Monday. Chamila Karunarathne / AP

Officials in Sri Lanka said the blackout of Facebook, YouTube, WhatsApp and other services was a temporary way to stanch the spread of false information after the bombings.

This approach — although it is sometimes driven by different motives — was once routine in countries like Turkey, Pakistan and Afghanistan, said Alp Toker, executive director of Netblocks, a nonpartisan, non-governmental group that monitors internet freedom.

"This kind of incident we would've tracked up to three times a month in 2016 and 2017," he said.

Then, Toker said, came a "turning point" — a series of coordinated bombings in Brussels that killed more than 30 people in 2016.

"The first responders used social media effectively to understand what was going on, where it was happening and how to counter the threat," he said.

Some of those countries appeared to take notice, and they cut down on post-attack shutdowns, he said. They also seemed to realize not only how popular the services were — and how shutdowns could easily trigger a backlash — but also how governments could use them for their own purposes.

"Authorities have the upper hand on social media," Toker said. "They're the law. They also have control over social media companies, and to some extent they can restrict content they don't agree with."

All of that has made the kind of social media blackout underway in Sri Lanka far less common than it was a few years ago, he said.

People used their mobile phones at the Francisco Fajardo highway, where they could get telephone service, during a partial power failure in Caracas, Venezuela, on March 9. Matias Delacroix / AFP - Getty Images file

But it's not as if it's unheard of. Three days before the bombings in Sri Lanka, the nonpartisan non-governmental organization NetBlocks documented restrictions on YouTube, Google applications and Bing in Venezuela. The blackouts occurred as the country's opposition leader, Juan Guaidó, was live-streaming an assembly speech in Caracas.

While not as targeted as the blackouts in Venezuela, the vast majority of internet shutdowns that Rydzak has documented over the last eight years also appear to have been driven by political motives, he said.

One of the first such large-scale shutdowns occurred in Egypt in 2011, when the government blocked the internet for three days during the Arab Spring uprising, Rydzak said.

Since then, other governments have embraced similar tactics. In Ethiopia's Oromia region, for instance, there were blackouts in 2016 amid deadly violence between anti-government protesters and security forces. In Sudan, the government blocked the internet for weeks as protesters targeted then-President Omar al-Bashir, he said.

In countries like Sri Lanka, where the government says it is blocking social media access to prevent misinformation that could lead to potential mob violence, the outcome can still be devastating, Rydzak said.

Governments "tend to claim they're conducted as security measures, but they actually block access to accurate information," he said. "They may also be means of concealing abuse by security forces and non-state actors."

Nor is there evidence that shutdowns prevent misinformation and violence, Rydzak said. Toker added that such "vacuums" can even accelerate the spread of false news.

"Those with technical expertise can get online, and they tend to be the people who are involved in producing content for commercial or political gain," he said. "The people who remain online can drown out the authentic voices from the scene of the incident."

Shutdowns can also keep people from reaching relatives and loved ones, Rydzak added, and they can drain local economies. According to NetBlocks, the estimated impact of shutting down WhatsApp, Facebook and Instagram is $4.1 million per day.

"That's pretty significant for a country where GDP per capita is less than $4,000," Rydzak said.