At least four oil tankers have been hit with explosions so far this year — all of them having visited Russia’s territorial waters in the weeks prior to the blasts happening.

A heavily-laden Russian oil tanker ran aground in the Baltic Sea in northern Russia on Sunday, according to media reports. In the latest incident involving a Russian vessel, the Koala was carrying 130,

The incidents are the first non-military ship explosions in the central Mediterranean in decades. On Feb. 15, ttwo explosions 20 minutes apart damaged the hull of the Greek-operated crude oil tanker Seajewel in the northern Italian port of Savona,

A series of mysterious explosions have hit oil tankers linked to Russian ports, sparking fears of escalating maritime conflict.