Greece has told its shipping fleet to adopt maximum security measures when sailing to Russian Black Sea ports after drone attacks on two Greek-operated tankers, reported Reuters.

Drones struck two oil tankers, including one chartered by US oil major Chevron, as they approached the Caspian Pipeline Consortium terminal on Russia's Black Sea coast.

Greece's shipping ministry advised vessels docked, anchored or preparing to dock at the terminal to take the highest possible precautions, including limiting crew movement outside the ship.

Greek-operated ships form one of the world's largest tanker fleets and are vital for Black Sea trade, which involves Bulgaria, Georgia, Romania, Turkey, Russia and Ukraine.

War insurance costs for ships sailing to the Black Sea have surged this week, reflecting heightened risks.

One of the targeted tankers, Matilda, managed by Greece's Thenamaris, was hit by two drones. A company official said no injuries or serious damage occurred, but crews have been instructed to increase vigilance and avoid unnecessary exposure.

The ministry referred to earlier advisories dating back to April 2022, which recommended protective measures for vessels calling at Russian Black Sea ports including Novorossiysk, Taman, Tuapse and Kavkaz.