bbc, Jonathan Marcus:

China is Russia's most important trading partner and some two-thirds of China's imports from Russia are oil or natural gas. This new deal only underscores this critical relationship.

It is an agreement that has been a long time in the making, with the Chinese hesitant about price. But of course the statistics tell only part of the story.

The deal comes at a time of growing tensions between Russia and the West, prompted in large part by the Ukraine crisis. And it is not just Ukraine: there are fundamental differences over Syria and about the whole direction in which President Vladimir Putin is taking his country.

Indeed, at times Mr Putin seems to be setting Russia up as an alternative pole in terms of what he appears to regard as the decadent values of the West.

Thus this deal between Russia's Gazprom and the China National Petroleum Corporation could symbolise an important moment of transition - when both in economic and geopolitical terms, Russia's gaze begins to look more towards the East rather than towards the West.

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