Russia has detained a Greek-owned oil tanker, Green Admire, while it was transiting through a designated maritime route from Estonia to Rotterdam, sparking fresh tensions in the Baltic and drawing concern from NATO allies.

The tanker, carrying Estonian shale oil, was stopped in Russian territorial waters near the island of Gogland, according to vessel tracking data from Marine Traffic. It had departed from the Estonian port of Sillamäe and was using an established corridor that crosses Russian waters, under an agreement between Estonia, Finland, and Russia.

“Today’s incident shows that Russia continues to behave unpredictably,” said Estonian Foreign Minister Margus Tsahkna. “I have also informed our allies about the event.”

The Estonian Foreign Ministry confirmed the incident and has since rerouted maritime traffic to avoid Russian waters. “Vessels entering and leaving the port will now be routed through Estonian territorial waters,” the Estonian Transport Administration announced.

The seizure comes just days after Estonia accused Russia of violating NATO airspace and intercepting a tanker believed to be part of Russia’s shadow fleet—a network used to bypass Western sanctions.

With tensions rising, the European Union is reportedly preparing new sanctions targeting Russia’s shadow fleet, Nord Stream-related infrastructure, and financial institutions.

This latest maritime confrontation underscores growing volatility in the region as NATO and EU leaders brace for further provocations.