China vowed Sunday to plough ahead on economic and diplomatic cooperation with Russia despite Western sanctions against Moscow over the conflict in Ukraine, stressing their relations are based on "mutual need".

"The practical cooperation between China and Russia is based on mutual need, it seeks win-win results and has enormous internal impetus and room for expansion," said Beijing's foreign minister Wang Yi.

As well as sanctions, Vladimir Putin's Russia is facing a sharp decline in its ruble currency amid an economic crisis fuelled largely by plunging oil prices.

Both countries are permanent members of the United Nations Security Council, where they have in the past jointly used their veto power against Western-backed moves such as in the civil war in Syria.

Wang told reporters on the sidelines of the National People's Congress, China's Communist-controlled parliament, that Beijing and Moscow will "continue to carry out strategic coordination and cooperation to maintain international peace and security".

Wang's comments signal that Putin, assailed by the West over the annexation of Crimea and the ongoing conflict in eastern Ukraine, can count on continued Chinese economic and diplomatic support.

Beijing and Moscow, allies and then adversaries during the Cold War, have over the past quarter century often found common ground internationally, frequently taking similar stands at the UN.

They have also forged increasingly closer economic ties, with China hungry for Russia's vast hydrocarbon resources. Western sanctions have made seeking stable markets an urgent need for Putin, whose economy has been hit hard by the fall in prices for oil, a major source of revenue.

Putin and Chinese President Xi Jinping, who met five times last year, have a close personal relationship.

Xi told visiting Russian foreign minister Sergei Lavrov in February that the two countries' "cooperation grows ever deeper".

In the economic arena, the two sides will "work hard" to increase bilateral trade to $100 billion, while intensifying cooperation in the financial, oil and gas and nuclear power sectors, Wang said, after China-Russia trade totalled $95.3 billion last year.

Among other results, he said they would begin "full construction" of an eastern natural gas pipeline and also sign an agreement on the western route.

Wang added that they would "accelerate joint development and research" on long-range wide body passenger jets, begin working together to develop Russia's far eastern region and step up cooperation on high speed railways.