Ukraine’s Unmanned Systems Forces said they carried out attacks on Russian vessels in the Sea of Azov over a 72-hour period, targeting 21 ships in total.

The force said the strikes hit 19 oil tankers it linked to Russia’s “shadow fleet”—sanctions-evasion vessels used to move fuel and other goods. It also reported damage or strikes on a dry cargo vessel and a ferry operating near Kerch.

Ukrainian commanders framed the operations as part of a continuing effort to disrupt Russia’s logistics and supply routes, particularly those supporting operations around the occupied Crimea region.