Sehan Jayathunga said he’s noticed an uptick in sales of an outmoded item at his father’s grocery store on New York’s Staten Island: international calling cards.

With a variety of modern communications channels blocked, he and other Sri Lankans are relying on the cards to reach family members on the other side of the world in the wake of the deadly Easter bombings in that country.

“Everybody has been buying because nothing else has been working,” Jayathunga, 24, said.

Sri Lanka’s government imposed a blackout on most social media services, including calling and messaging apps such as WhatsApp, shortly after the series of bombings at churches and hotels killed hundreds in the predominantly Buddhist island nation off the southern tip of India.

Jayathunga said an aunt and a cousin were close enough to one of the blasts to hear and feel it, but that after the attack, he and other relatives in the United States couldn’t reach them.

“Viber, WhatsApp ... none of that was working,” he said. But the phone cards — which were a staple for making long-distance and especially international calls before the rise of internet-based telephony and later smartphone apps — did work. “We tried with the phone line,” he said.

The Sri Lankan government’s restrictions, which it says are a temporary way to stop the spread of extremist material, are stoking frustration and worry among Sri Lankans and their families living abroad in the U.S. and elsewhere.

Like others worldwide, they’ve grown accustomed to staying in touch with friends and family via quick and almost free international communication from an array of apps that don’t have calling charges or texting fees.

“I was really scared. I hadn’t had a clue of what to do,” Desha Perera, 41, said in a phone interview from London, where she works in sales. “Every day, I’m talking with them on Viber and WhatsApp,” she said of family in Sri Lanka.

Like others, she tried an international phone card when none of the apps worked, and she said she felt relief only later Sunday when she was able to reach her 75-year-old father and 73-year-old mother.

Phone cards may not be the only way to get around the Sri Lankan government’s restrictions. Julia Wijesinghe, 20, a Sri Lankan American and founder of the Staten Island-based Sri Lankan Art & Cultural Museum, said her family has been able to circumvent them using a virtual private network, or VPN.

Sri Lanka’s blackout of social media was widely condemned by human rights organizations as a violation of free expression, and they used the hashtag #KeepItOn to try to rally an international outcry.

“Many in Sri Lanka rely on social media platforms and messaging apps to reach out to their families. Around the world, relatives and friends are checking to see if their loved ones are okay. For those in danger, and for those who want to help, not being able to connect or confirm that a loved one is safe can be devastating,” the group Access Now said in a statement.

Cutting off communications can also block emergency services, the group warned, citing a January attack by gunmen in Kenya in which survivors credited WhatsApp, which is owned by Facebook, and other services with helping to save lives.

We have managed to make contact with some of our Nursing colleagues in Sri Lanka and let them know that we stand in solidarity with them, all healthcare workers and the people of Sri Lanka @ICNurses will follow up in the coming days — Howard Catton (@HowardCatton) April 22, 2019

Facebook said it was working to support first responders and to remove material from its services that violates its rules in Sri Lanka. The company also said it wanted to keep its services available despite the government restrictions.

“We are aware of the government's statement regarding the temporary blocking of social media platforms. People rely on our services to communicate with their loved ones and we are committed to maintaining our services and helping the community and the country during this tragic time,” Facebook said in a statement.

Freedom House, an organization that advocates for free expression, said it was alarmed that some governments had come to see the practice of blocking communication tools as normal.

“By cutting off service during such incidents, governments deny their citizens access to communication tools at a time when they may need them the most, whether to dispel rumors, check in with family members, or avoid dangerous areas,” Freedom House said in a statement.

At least 21 countries have blocked social media at some point since 2017 and at least 13 countries disconnected the internet altogether, according to Freedom House’s tally. India topped the list of most frequent internet shutdowns with 130 reported incidents in 2018.

Complicating the situation is a rising international tide of anger at social media companies such as Facebook, YouTube and Twitter for not doing more to halt the spread of violent or extremist material. Governments across the world have been crafting new laws to impose liability on the companies for failure to take down certain content.

So far, human rights groups are standing by the tech companies in their fight against possible regulation, though public sentiment about social media has shifted.

Perera’s daughter, Linasha Kotalawala, 21, said she could understand the Sri Lankan government’s reasoning for what it had done in the face of misinformation.

“I felt shocked, but then I realized that maybe this was a reasonable thing that the government imposed,” said Kotalawala, a student studying economics and politics at Goldsmiths, University of London.