Britain said on Thursday it had sanctioned five ships and two other shipping entities under its Russian sanctions regime.
Earlier this month Britain slapped sanctions on 10 further ships in Russia's so-called "shadow fleet" of vessels which it says use illicit practices to avoid Western restrictions on Russian oil, Reuters reported.
Russia rejects Western pressure to limit its oil exports, and in the past year there has been a growth in the number of tankers transporting cargoes that are not regulated or insured by conventional Western providers.
Thursday's sanctioned entities were White Fox Ship Management and Ocean Speedstar Solutions OPC. The ships were Asya Energy, Pioneer, North Sky, SCF La Perouse and Nova Energy.