A video released by the so-called Islamic State (IS) on Sunday shows the interrogation and execution of two men that the group claims had secretly worked against it, presenting the latest and most graphic evidence of its brutal crackdown on local activists in its self-proclaimed capital of Raqqa in Syria.

Filmed in the group's now familiar saturated and slow-motion style, the IS video, which was viewed by VICE News, depicts the two young men — identified as Faisal Hussain al-Habib and Bashir Abduladhim al-Salem (who has been referred to as al-Saado in some reports) — as they confess to alleged crimes against the terrorist insurgency. They recount spying on IS activities and taking photographs of its members in the Syrian towns of Rumaila, Tal Abyad, and al-Wadi.

The two men say that Hamoud al-Mousa, who is part of the team that founded the activist network Raqqa is Being Slaughtered Silently (RSS), instructed them to smuggle materials out of IS territory. Mousa, they said, gave them a watch and pair of glasses that could surreptitiously take photographs.

After their interrogation, the two men are shown tied to trees in the dark. Camouflaged commandos approach the men, vested in orange jumpsuits, and shoot them directly in the head. The men slouch, as blood streams from the bullet wounds.

RSS did not immediately reply to questions regarding the video, but Abu Mohammed, a media activist with the group, told the International Business Times that the men did not in fact work for them.

"I don't know whether they are activists," he said. "Reports came out saying they were working with us, but that is not true. I'm surprised by these reports."

On June 24, RSS reported that IS had begun "a campaign of raids and arrests" in the previous two days that targeted young men in Raqqa, which is the headquarters of the dubious caliphate that the group declared in the stretches of territory it controls in Syria and Iraq. Roughly 25 young men were taken into custody. It is unclear if Saado and Habib were captured during this time.

The crackdown coincided with a series of military setbacks suffered by IS at the hands of Kurdish and Arab rebel forces, which included the loss of Tal Abyad, a strategically vital town on the border with Turkey.

RSS said in a statement that its members were not likely to fall victim to IS roundups, which it said entailed, in part, entrapment schemes at internet cafes that attempted to catch users "liking" the RSS Facebook page.

Despite its confidence in the face of such crackdowns, RSS has lost members in the past year. On May 7, one of its members, Moataz Bellah Ibrahim, was arrested and killed by IS as he attempted to flee from Tal Abyad toward Turkey. RSS claimed that IS didn't learn of Ibrahim's true role in the network until after his execution, however.

"The campaign did not lose after this incident none of its members, whether by execution or even just arrest or detention by the organization," RSS said in its report last month. "Members are still exercising their usual activities at home and abroad, and they have had not been subjected to any little harm."

Patrick Skinner, director of special projects at the Soufan Group, which tracks extremist groups, told VICE News that there was no way to know precisely what activities the two men in the latest video had engaged in, or whether they were just strawmen for an increasingly paranoid IS to use in an information war against activist networks in Raqqa.

Skinner said IS finds itself uniquely vulnerable to spying, given their self-proclaimed conception as a "state," with bureaucratic and military operations.

"It's clear that they have a problem," said Skinner. "They are in the open, and that presents them as a target for espionage."

Skinner said that IS grew increasingly paranoid after US special forces were able to target and kill Abu Sayyaf, a figure in the militant group that American authorities claimed helped oversee the its financial activities. That attack, which took place in May, would have had to rely on local intelligence in order to deploy Special Forces accurately, he said.

Meanwhile, RSS has long been able to post photographs on their social media accounts taken from inside Raqqa.

"Whenever IS is under pressure, they feel they have to ramp up these graphic executions to try to terrify anyone from spying against them," said Skinner. "They make sure it's dramatic, like this slow-motion execution."

On Sunday, IS posted a video depicting the execution of 25 Syrian government soldiers amid the ruins of the ancient city of Palmyra. The footage, which reportedly was filmed last month, also coincided with the recent military setbacks elsewhere in Syria. Experts have long pointed out the delay in releasing such graphic videos, or of footage showing the destruction of antiquities, as a timed effort to rally IS forces and demonstrate their control.

But in this case, Skinner noted, "we don't know who these two poor people were."