Russia has so far deflected much of the impact of sanctions on its oil trade, but the insurance industry threatens to throw a spanner in the works unless Moscow and its customers can plug a gap left by Western underwriters.

Insurers from Europe and the United States, which dominate the international marine market, are curtailing coverage for Russian oil tankers, industry sources say, to avoid breaching sanctions imposed in the wake of Moscow's invasion of Ukraine. Even non-Russian vessels are now at risk of being dropped by Western insurers if they carry Russian crude.

The moves by Western insurers could undermine Moscow’s recent success in rerouting supplies of crude from Europe and the United States to Asia, accelerate the decline in its European business and blow a bigger hole in energy markets as restrictions ensnare the world’s second-biggest crude exporter.