Four gunmen are among 11 people arrested following a shooting massacre in a packed Moscow concert hall, according to Russia's President Vladimir Putin, according to SkyNews.
Videos broadcast on Russian media appear to show the detention and violent interrogation of the suspects.
In one piece of footage a man was marched out of a forest, his face covered in blood from what appeared to be an ear injury, before struggling to speak in Russian.
Another video showed a man trembling on his knees as he answered in heavily accented Russian to a series of barked questions.
He was initially shown lying on his stomach with his hands bound behind his back, his chin resting on the boot of a figure in camouflage uniform.
The men were from Tajikistan, according to Russian news reports.
The former Soviet country is in Central Asia, predominantly Muslim, and borders Afghanistan.
Mr Putin has claimed the gunmen attempted to flee to Ukraine in the aftermath of the mass shooting, in which at least 133 people were killed.
The allegation came despite the Islamist terror group Islamic State Khorasan (IS-K) claiming responsibility for Friday night's attack.
"They tried to hide and moved towards Ukraine where, according to preliminary data, a window was prepared for them on the Ukrainian side to cross the state border," Mr Putin said of the suspects.
But neither he nor the FSB publicly presented proof linking the attack to Ukraine, which it invaded 25 months ago.
His words were met with derision from Ukrainian President Volodymyr Zelenskyy, who said it was "absolutely predictable" that "Putin and other scum are just trying to blame someone else".
The thousands of Russians dying on Ukrainian soil would be better used stopping terrorists at home, said Mr Zelenskyy.
"They [Russia] drove hundreds of thousands of their terrorists here, on Ukrainian soil.
"They are fighting against us and they don't care what happens inside their own country."
