Finland has seized an oil tanker suspected of having severed undersea power and internet cables, with Finnish authorities saying the vessel may have been part of Russia's "shadow fleet" of ships aimed at skirting Western sanctions.

Police and media reports say that Finnish authorities have detained a Russia-linked ship as they investigate whether it damaged a Baltic Sea power cable and several data cables.

Finnish authorities said on Saturday they are moving an impounded tanker closer to port after boarding the vessel carrying Russian oil earlier this week on suspicion it had damaged an undersea power line and four telecoms cables.