Ukraine's security service, the SBU, has released a recording of what it claims are phone conversations that it intercepted between "subversive groups" of Russian servicemen deployed in eastern Ukraine and their bosses in Moscow.
In the recording published on the service's YouTube channel on Monday — a day after Ukraine's interior minister said a security officer was killed and five others wounded in a gun battle to the east of the country — a supposedly Russian agent said that his group had "taken out" several people when a motorcade ran into their ambush.
"Our group shot down three VIP-class vehicles in which they were traveling," he added.
The unidentified caller on the other end of the line praised the assault and cited Ukraine's official statements, which said that the head of the security service's counter-terrorism task force was among those injured during the Sunday shootout in the eastern city of Slovyansk.
"You marked the holiday well," he said at the end of the call, in an apparent reference to Palm Sunday, a Christian holiday celebrated in both Russia and Ukraine.
In another of the phone calls, the SBU video cited a Moscow phone number for one of the callers, identified only as "Alexander" in the video.
Ukrainska Pravda reported that the number belonged to a pro-Kremlin publicist Alexander Borodai, and cited unidentified sources as saying that the man had been entrusted with the "Crimea question" and now is handling the "Donetsk question" in eastern Ukraine. In February, Borodai published a YouTube video, titled: "How to Divide Ukraine."
The SBU said in a statement that Russia had begun "large-scale military aggression" in eastern Ukraine by deploying "subversive groups" of servicemen from elite military units.
The Russian Defense Ministry has denied any military intervention, and accused Kiev on Monday of putting together the recording in a "cheap attempt" at a cover-up for a supposedly botched anti-terrorism operation, RIA Novosti reported.
Other videos posted on YouTube this weekend showed well-armed men in military fatigues directing pro-Moscow protesters during a storm of a police station in the eastern Ukrainian city of Kramatorsk, and leading raids in other towns.
Western diplomats cited the footage as evidence of a replay of the scenario that preceded Russia's annexation of Crimea, when armed men in uniforms without insignia took control of the peninsula, while Moscow denied that they were Russian.
"You don't have to take my word for it, or even those of the Ukrainian government. You need only witness yourself the videos of professional military shepherding thugs into a building in Kramatorsk, the photographs showing the so-called concerned citizens taking over Slovyansk equipped exactly like the elite troops that took Crimea, or the video of a military operation in Krasny Liman by armed men with the same equipment," U.S. Ambassador to the UN Samantha Power said Sunday in comments posted on the U.S. diplomatic mission's website.
British Ambassador to the UN Mark Lyall Grant said that the video footage showed "a pattern that is all too familiar."
Russian President Vladimir Putin spoke by phone with his U.S. counterpart Barack Obama on Monday and denied accusations that Russia was involved in the escalating violence in eastern Ukraine, the Kremlin said in a statement.
Instead, he blamed the unrest on the "unwillingness and the inability of the Kiev leadership to take into consideration the interests of the Russian and Russian-speaking population."