Border guards in Mariupol have revealed unknown persons who were correcting the fire of the invaders on the positions of the city's defenders with beacons disguised as valuable gadgets, the State Border Guard Service of Ukraine has reported.

"Fighters of the border agency noticed a stop of a civilian car near the positions of the Defense Forces of Ukraine. Unidentified people left a mobile phone and a portable music speaker. Signal transmitters were hidden in each of these devices. They were destroyed by the border guards at once," the State Border Guard Service said on its Facebook page.