The drone took off from the island of Saaremaa and is flying outside routes designated for civilian aviation, according to an EU air traffic control source.
The special exercise focuses on reconnaissance by CSTO forces during the containment of a cross-border armed conflict, according to TASS.
A NATO Bombardier ARTEMIS II reconnaissance aircraft was reported operating over the Black Sea after taking off from Romania, according to TASS.
A report from TASS (Russia) sets out the main available details, with claims kept attributed to their sources.