China's imports of oil from Russia rose 55% in May, customs data showed on Monday, despite the West sanctioning fuel imports from Moscow over the war in Ukraine.

China, the world's second-biggest economy, imported around 8.42 million tonnes of oil from Russia last month, surpassing its shipments from Saudi Arabia.

Last week, Chinese President Xi Jinping assured his Russian counterpart, Vladimir Putin, of China's support for Russian "sovereignty and security."

Beijing has been accused by the West of providing diplomatic cover for Moscow by blasting Western sanctions and extensive arms sales to Kiev.

The customs data comes four months into the war, with other buyers avoiding Russian energy imports.

The number was also a spike from the 5.44 million tonnes China imported in May 2021, according to figures from the Customs Administration, and helped Russia overtake Saudi Arabia as China's main source of oil.

Earlier this month, Chinese state media pointed out that Beijing was willing to "intensify strategic coordination between the two countries."

The Kremlin said the two leaders had agreed to ramp up economic cooperation in the face of unlawful Western sanctions.

The West has adopted unprecedented sanctions against Russia over the war in Ukraine. The United States has banned Russian fuel imports, while the United Kingdom and the European Union have agreed to phase out their use.

However, Russia earned around $20 billion from oil exports in May, resuming pre-war levels in a setback to Western efforts to suppress its economy.

Asian countries such as China and India have increased their imports of Russian fuel, lured by record discounts of more than 30% on Brent crude.