Ukraine's domestic security agency, SBU, posted a one-and-a-half-minute audio recording on its Telegram channel in which two men are heard discussing in Russian the aftermath of the dam collapse.

"The invaders wanted to blackmail Ukraine by blowing up the dam and staged a man-made disaster in the south of our country."

Meanwhile, seismic data picked up by the NORSAR observatory in Norway showed activity at 2:54 a.m. local time on June 6 indicating an explosion -- with the timing of the explosion coinciding with media reports of the dam collapse.

"The signal that we are analyzing, the way the energy is recorded on the sensors at distance, clearly shows us that this is an explosive-type character compared to many other explosions that we monitored in the past," Volker Oye, head of research at NORSAR told Reuters on Friday.