Wang Kangpeng, an analyst with sinoergy.com, a Beijing-based energy industry consultancy, said energy industry relations between China and Russia used to focus solely on oil and gas trading.

But that is now likely to widen after these most-recent transactions, which he said represented a more comprehensive partnership between the nations, said Wang. In particular, he said, the Rosneft-ChemChina agreement is likely to help it expand its downstream market by bringing more value to its refining businesses.

"This will greatly help the company reduce its exposure to global crude price fluctuations and the effect of sanctions by the United States and Europe," Wang said.

Also during Putin's visit, Russia's natural gas developer OAO Gazprom signed a third project memorandum with China National Petroleum Corp, part of an overall strategic cooperation over the next five years.

The base for the gas supplies to China from the Russian Far East will be Sakhalin, a large Russian island in the North Pacific Ocean, according to Gazprom Chief Executive Aleksey Miller.

However, the volume and timing of the new route have not been decided yet.

Elsewhere, China and Russia also signed a 30-year contract for gas supplies to China through a western route, which followed an earlier $400 billion deal that will deliver 38 billion cubic meters of gas to China annually through an eastern route, starting in 2018.

Liu Qian, an analyst with the Academy of Chinese Energy Strategy at the China University of Petroleum, said more Sino-Russian energy agreements are expected in the future.

China's third-largest energy player CNOOC Ltd, which has been focusing on offshore oil and gas production, is the most likely to sign further deals with Russian companies, Liu said.

Yang Hua, chairman of CNOOC, has met with Igor Sechin, president of Rosneft in late August.

Liu said the two companies did not release anything formal afterwards, but he was told by Russian officials that they considered CNOOC as having the best financial performance of China's "big three" energy giants.