BEIJING (Reuters) - A vaunted 'new era' of strategic partnership between Russian President Vladimir Putin and his counterpart Xi Jinping begun in Beijing on Thursday may not exactly have been sealed with a kiss, but it did lead to rare hugs between them.

Russia, grappling with Western sanctions after its invasion of Ukraine, is increasingly reliant on its booming trade with China, which is challenging U.S. supremacy in areas from quantum computing to espionage and hard military power.

Although President Xi, in keeping with the tenets of China's political culture, is not known for effusive displays of warmth, he gripped Putin by the shoulders and hugged him twice.

Footage from state broadcaster CCTV showing the leaders embracing in the evening air of the Zhongnanhai leadership compound in the Chinese capital appeared to be popular on social media. Aides and officials stood by, some clapping.

They were concluding an informal tea and dinner event considered to be the key session of Putin's two-day visit to China.

Putin then flew to the Russian-influenced city of Harbin in the northeast, where he was due to spend Friday before returning to Moscow.

Hours earlier the leaders had signed a lengthy statement that sharpened their opposition to a U.S.-led world order and pledged co-operation across fields ranging from space and nuclear technologies to finance and manufacturing.

"The China-Russia relationship is hard earned, and the two sides need to cherish and nurture it," Xi said.

And while Putin hailed their "warm and comradely" talks, their embrace still stopped well short of the full "socialist fraternal kiss" favoured by leaders such the Soviet Union's Leonid Brezhnev at the height of the Cold War.

(Reporting by Beijing newsroom; Writing By Greg Torode; Editing by Clarence Fernandez)