DUBAI (Reuters) – Islamic State has issued a video showing the beheading of what it described as a Russian intelligence officer captured in Syria, the U.S.-based SITE monitoring website reported on Tuesday.

The Russian Defence Ministry and the FSB security service were not immediately available for comment, but a Russian senator said that “there will be hell to pay” if the recording was proven to be authentic.

The 12-minute Russian-language video, released on the day Russia celebrated the anniversary of the 1945 victory over Nazi Germany with military parades, showed the man dressed in a black jump suit kneeling in a desert scene and urging other Russian agents to surrender.

“This idiot believed the promises of his state not to abandon him if he was captured,” a narrator says in the recording, before being beheaded by a bearded man dressed in combat fatigues.

The authenticity of the recording and the identity of the man could not immediately be verified, nor was it clear when the killing occurred.

Russian senator Viktor Ozerov, who heads the defense committee in Russia’s upper house of parliament, said the defense ministry would check the authenticity of the video.

“Even if it is a fake, it shouldn’t be left without attention,” Ozerov told Russia’s Interfax news agency. “If it happened, then there will be hell to pay.”

Russian forces are backing Syrian President Bashar al-Assad in his war with rebels and militants seeking to oust him. The video showed scenes of what it described as the aftermath of Russian bombing raids in Syria.

The Russian defense ministry says about 30 Russian servicemen have been killed since the start of the Kremlin’s operation there in September 2015.

(Reporting by Sami Aboudi in Dubai and Alexander Winning in Moscow; editing by Ralph Boulton)