These are the two Zubr-class LCACs (NATO reporting name: "Pomornik") of the Russian Navy: 770 Evgeniy Kocheshkov and 782 Mordoviya, based in the port of Baltiysk. These soviet-designed amphibious ships were built to land amphibious assault units on beaches.
They can also transport and plant naval mines. Powered by three propellers, they can carry up to 150 tons, i.e. up to 500 men, or land equipment such as armored vehicles and tanks.
Preligens' vessel detector spots them here in the port of Baltiysk and allows permanent monitoring of their activity.