https://www.reuters.com/world/europe/estonia-says-russia-detained-tanker-baltic-sea-2025-05-18/Russia has retaliated against the Estonian attempt to seize one of its tankers (Russian fleet, but Gabon flagged or whatever) in international waters a few days ago (thwarted when Russia scrambled a jet into Estonian airspace above international waters, the maritime borders are complicated)
Russia has now seized an oil tanker leaving an Estonian port (Greek owned, Liberia flagged).
Quote
Russia has detained a Greek oil tanker sailing under the Liberian flag as it left the Estonian port of Sillamae on a previously agreed route through Russian waters, the Estonian Ministry of Foreign Affairs says.
In a statement published on Sunday, the ministry added that the vessel, the Green Admire, was undertaking a navigational route established in a deal between Russia, Estonia and Finland.
The Baltic nation will redirect traffic to and from Sillamea exclusively through Estonian waters to prevent similar incidents in the future, it added.
“Today’s incident shows that Russia continues to behave unpredictably,” Foreign Minister Margus Tsahkna said. “I have also informed our allies of the event,” he said, referring to other NATO members.
Estonian Public Broadcasting (EPB), citing the Transport Administration, reported that the Greek tanker was carrying a cargo of shale oil destined for Rotterdam in the Netherlands. It added that such incidents had never occurred before.
Refer to the map I posted 2 pages ago. Sillamae is just west of Narva on that map, and there is a route through Estonian waters but presumably traffic in peacetime is
supposed to travel along that international waters path and cut towards the ports, so you'd have to zig zag to avoid the Russian territorial waters that juts out. IE sail to the edge of Russian waters, cut towards Kunda, travel the coast to Sillamae. Instead they used a "previously agreed route through Russian waters". Which the Russians agreed to before Estonian started harassing them.