After news broke Friday that a military coup was under way in Turkey, people around the world quickly looked to social media sites like Facebook and Twitter to find out if it was true, and to find out who was in control of the government in Ankara.

But in Turkey, people were not able to find that information on their social networks. Access to Twitter, Facebook and Google’s YouTube was quickly restricted, or only intermittently available, according to various watchdog groups.

Dyn, an internet performance management company that has servers located in Turkey, said that it saw Facebook and Twitter access slow to a crawl in the country.

“It wasn’t like an outright block, like they’ve done in the past,” Doug Madory, director of internet analysis at Dyn, said in an interview. “They’re throttling the speed of these sites to the point of complete unusability.”

TurkeyBlocks, an organization that tracks internet access in the region, tweeted that access to Twitter, Facebook and YouTube was blocked in Turkey at 10:50 p.m. local time after reports of a military uprising began. And Cloudflare, a company that does web security, said it had seen internet traffic out of Turkey drop 50 percent as of late Friday.

In a post sent from its official policy account on Friday, Twitter confirmed some of the early reports of a slowdown in its service in Turkey.

“We have no reason to think we’ve been fully blocked in #Turkey, but we suspect there is an intentional slowing of our traffic in country,” the company said.

A spokeswoman for Facebook declined to comment. YouTube said in a statement that while the company was aware of reports of its service being down in Turkey, its systems later appeared to be functioning normally.

The Turkish government has a long history of blocking access to digital communications services in times of crisis. After a hostage situation in Istanbul last year, for instance, Turkish authorities blocked Twitter and YouTube throughout the country in an attempt to curtail the spread of photographs of the situation.

“Turkey blocks and throttles social media wholesale when accurate information is needed most — after terror attacks, during corruption scandals, and now, apparently, military coups,” said Peter Micek, global policy and legal counsel for Access Now, a nonprofit digital rights group.

The blocking is done primarily by manipulation of domain name systems in Turkey, according to Mr. Micek; domain name systems are a kind of digital directory of the various websites and computers connected to the internet. Mr. Micek noted that worldwide, Access Now has seen such shutdowns more than 25 times globally in 2016, three of which have occurred within Turkey.

Slowing down access instead of an outright block appears to be an evolution of the government’s techniques, said Mr. Madory of Dyn. The method leaves some room for ambiguity over what is occurring, and who is responsible for the slowdown.

“This seems to be the new way of restricting communication access around the world,” Mr. Madory said. “Authorities don’t make an explicit block of these websites, but it’s pretty clear to us what’s being done.”