Dozens of pro-ISIS Twitter accounts appear to have been suspended in the social networking site's latest purge of online extremists. The crackdown follows the Sunni militant group's release of another video showing British hostage John Cantlie, although it was not clear if that prompted the cull. "It’s definitely been one of the heaviest weeks [for suspending pro-ISIS accounts] ever," Belgium-based historian and blogger Pieter Van Ostaeyen told NBC News. He said least 77 accounts he followed were suspended.

Twitter, like Facebook and YouTube, has been actively engaged in combating ISIS and its sympathizers as they post gruesome footage and propaganda. Web intelligence firm Recorded Future said 28,000 pro-ISIS accounts were set up in the 14 days after the videoed beheading of U.S. journalist James Foley. "This has somewhat disrupted their propaganda distribution mechanism, but not really," NBC News terrorism analyst Evan Kohlmann said. "It just takes a few hours more for the media to go viral, but it always does. Nobody has managed to really stop ISIS from releasing new beheading videos." In a statement, Twitter said: "We review all reported accounts against our rules, which prohibit unlawful use and violent threats."

In-Depth

SOCIAL

That's at least 1,300 suspensions in the last 30 days, compared to 400 in seven hours. Big move. — J.M. Berger (@intelwire) September 30, 2014

- Alexander Smith