"Many VLCCs [very large crude carriers] discharged into government tanks in November," said an industry source based in the east coast city of Ningbo, where the tanks are located.

The shipments come after the country's initial strategic stockfill in August and provide further evidence that the world's second-largest energy consumer is building up an emergency buffer with additional imports, which analysts say have helped support oil prices.

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Two sources, familiar with how imported crude supplies are divided between a local refinery, the domestic pipeline system and the government- owned tank storage, named five supertankers that were diverted into the state stockpile last month.

Of the total, 2.5 million barrels on two tankers were Oman crude, and one tanker of about 1.9 million barrels each came from Yemen, Russia and Kuwait, one source said. Crude traders had speculated that some of the additional barrels could be from Oman after top refiner Sinopec, the largest single buyer of Omani crude, was seen lifting around eight million barrels of the grade for November loading, more than its usual four to six million.

It was unclear whether the move was part of Beijing's long-term energy strategy to provide an emergency buffer amid rising imports or a commercial move by Sinopec, which has leased 10 million barrels of capacity for its own use as the government debates policy.

The incoming crude follows a fill in August of around three million barrels of Russian Urals crude.

The new imports suggest that the facility now holds at least 11 million barrels of crude, giving China a fall- back position in case of a supply disruption.

Western nations worry that Beijing will use the stocks more frequently and liberally than industrialized nations, buying when prices are low and releasing stocks when oil rises in an effort to temper prices. REUTERS