Tokio Marine & Nichido Fire Insurance Co, Sompo Japan Insurance Inc and Mitsui Sumitomo Insurance Co started notifying shipowners about their decision on Friday, the business daily reported.The Sakhalin Island complex, partly owned by Gazprom (GAZP.MM) and Japanese companies, is vital to Japan's energy security as it accounts for 9% of the country's LNG imports.The three Japanese insurers will likely start negotiating with reinsurance companies after the Christmas holidays on possibly restarting coverage, the Nikkei said.Almost all vessels obtain ship insurance, and without additional coverage for Russian waters the area would be too risky for navigation, the Nikkei said.In February, London's marine insurance market added the Ukrainian and Russian waters around the Black Sea and Sea of Azov to its list of areas deemed high risk as tensions persist in the region."