The Islamic State, the violent extremist group that espouses a return to a seventh-century caliphate, has been astonishingly successful at spreading its message using 21st-century social media, according to a study released Thursday.

Despite repeated attempts by Twitter to thwart the Islamic State’s threats, propaganda and online recruiting by suspending accounts associated with the group, sympathizers have maintained thousands of active accounts on the social network, the study said. The users include a disciplined core group that sends messages frequently and understands how to maximize its effect.

"Jihadists will exploit any kind of technology that will work to their advantage," said J.M. Berger, an expert on online extremism who was the lead author of the study, a collaboration of the Brookings Institution and Google Ideas. But the Islamic State, he said, "is much more successful than other groups."

The release of the study came as Twitter, the San Francisco-based social media giant with more than 288 million active users worldwide, has moved more aggressively to suspend accounts linked to the Islamic State.

The group, also known as ISIS, which is ensconced in parts of Syria and Iraq, has used the social network to publicize executions of prisoners, including beheadings and at least one immolation, and to espouse death, violence and hatred for all perceived enemies.

Twitter’s crackdown on the group has led to death threats against the company’s leaders and employees.

Berger said the threats against Twitter reflected, to some degree, the Islamic State’s increased reliance on open social media forums, a Western invention that seems incongruous with militants’ desire for restoring the caliphates that once ruled vast areas of the Middle East.

The 92-page report found that a minimum of 46,000 Twitter accounts operate on behalf of the Islamic State. The study, titled "The ISIS Twitter Census," was the first public attempt to measure the influence of Islamic State members or their sympathizers on social media.

"ISIS has been able to exert an outsized impact on how the world perceives it," the study said.

The report also asserted that at least 1,000 accounts supportive of the Islamic State, and possibly many more, were suspended by Twitter between September and December.

Executives at Twitter, which did not provide assistance for the report, said the study had significantly underestimated the number of suspensions. They declined to comment on the report’s specific findings.

But the company said in a statement, "We review all reported content against our rules, which prohibit unlawful use and direct, specific threats of violence against others."

The group began posting videos of hostage executions and other atrocities last fall, generating a frenzy of media attention and speculation about its online propaganda and support.

The accounts in the study were observed from September through December and were analyzed based on criteria such as the number of messages, number of followers, hashtags and other identifying data, including the timing of messages, the language and, in many cases in which a mobile telephone was used to post a message, the geographic coordinates of the sender.

After further refining and filtering for deceptive practices, including the use of bots — computer software that creates fictitious activity on a social media account — the authors came up with between 46,000 and 70,000 accounts, but said "we believe the truth is closer to the low end of the range."

While these accounts have an average of about 1,000 followers each, considerably higher than an ordinary Twitter user, many followers also are account holders, which creates a kind of echo chamber in the messaging. Berger said that effect was likely to increase after Twitter suspended so many accounts.

While he and others have criticized Twitter for allowing the Islamic State to exploit its platform, Berger said a crackdown is "easier said than done."

With 288 million accounts, he said, "you don’t have the manpower to go into every one of their accounts and determine their origin."

The study said that the reach of even the most popular Islamic State account paled in comparison to the influence of celebrities or Western officials. President Barack Obama, for example, has 56.4 million followers. John Legend, the singer-songwriter, has 6.6 million.

"While highly active and committed, ISIS supporters are an insignificant speck in the overall sea of Twitter’s active monthly user base," the study said.

Berger said the monthly Twitter traffic from accounts linked to the Islamic State represented maybe one or two one-hundredths of a percentage point of the network’s total.

"We really give these guys a lot of oxygen for the size of their presence," he said.

Some of the group’s success on Twitter, the study said, reflected coordinated strategies by users, including the repeated tweeting of the same content by the same user within a short period of time, and the tweeting of the same content by a core group of about 2,000 users.

"To have that many accounts in a very disciplined way out there doing the same thing every day is a pretty powerful tool," Berger said. "It doesn’t sound like it’s that much, but it’s very difficult to get that many people who are that committed."

Twitter did not dispute an ABC News report that the company had recently shut down 2,000 accounts linked to the Islamic State.

Like other social media companies, Twitter suspends an account only after other users have reported abuses or threats prohibited by the company’s rules. Twitter says far more complaints are coming in now, prompting reviews of accounts that might previously have avoided scrutiny.

Scott Galloway, a professor of marketing at New York University and the founder of a research firm that studies brand influence on social media, said that while he has not assessed the data surrounding Islamic State activity on Twitter, the group’s influence is probably much bigger than the numbers would suggest.

Just as a celebrity’s popular Twitter message is often picked up and rebroadcast by other sites and news media, the violent imagery put out by the Islamic State receives wide distribution beyond its initial audience, Galloway said.

"The thing that is scary about ISIS is that they have clearly taken content production to a level of quality beyond other terrorist groups," he said. "The videos they have produced are the production quality of MTV."

"Great content will get distributed and shared beyond the control of any authorities," he said. "I think a ton of people are seeing this content."

© 2015 The New York Times Company