ISIS supporters threaten Mark Zuckerberg, Twitter's Jack Dorsey

ISIS supporters have a new target in their sights: the leaders of two of the world's most popular social networks.

The "Sons Caliphate Army," a group of hackers associated with the militant Islamic group, posted a video Tuesday that shows photos of Facebook's Mark Zuckerberg and Twitter's Jack Dorsey engulfed in flames and as targets for bullets. The 25-minute video, titled "Flames of the Supporters," is said to have been authenticated by Storyful, a startup that focuses on verifying news coming from the social Web.

The two tech leaders are apparently being singled out for their efforts to combat terrorist activities on their respective social networks. Both Facebook and Twitter in recent months have announced campaigns to eliminate activities by Islamic State extremists on their platforms by suspending accounts and deleting posts that promote violence and terrorism.

The stepped-up policing came about a month after a handful of leading tech companies met with top federal law enforcement and security officials in Silicon Valley to discuss combating terrorism. The meeting was called after attackers inspired by the Islamic State killed more than 130 people in Paris and 14 people in San Bernardino, California.

With hundreds of millions of people logging in each day, Islamic State and other radicals have found social media to be a fertile recruiting ground. In response, social networks have increased the size of teams overseeing posts and traffic.

Twitter, which has 320 million monthly active users, said earlier this month it had suspended more than 125,000 accounts since mid-2015 "for threatening or promoting terrorist acts, primarily related to ISIS." After the massacre in San Bernardino, Facebook removed the profile belonging to Tashfeen Malik, one of two shooters in the attack, for violating community standards. Facebook prohibits any praise or promotion of "acts of terror."

The video seeks to demonstrate that hackers still have access to accounts on the social networks despite efforts by Facebook and Twitter to banish them.

"You announce daily that you suspend many of our accounts, and to you we say: Is that all you can do? You are not in our league," text on the video clip reads, according to Vocativ, which first spotted the video. "If you close one account we will take 10 in return and soon your names will be erased after we delete your sites, Allah willing, and will know that we say is true."

Showing accounts that display Islamic State imagery, the video claims that ISIS-associated hackers have control of more than 10,000 Facebook accounts, 150 Facebook groups and more than 5,000 Twitter profiles.

"Many of these accounts have been given to supporters," the video says.

Twitter declined to comment, and Facebook representatives did not respond to a request for comment.