Still, China remains vital to Moscow's post-sanction survival, with Beijing buying discounted Russian oil and gas, shielding pro-Kremlin narratives on its tightly controlled internet, and exporting dual-use technology. U.S. and European officials have repeatedly accused Chinese companies of helping Russia sustain its military-industrial complex.

US Secretary of State Marco Rubio described Sunday's attack, which killed 34 people and injured 117, as "horrifying".

Russia issued a massive attack that claimed at least 34 civilian lives in Ukraine over the weekend. The strike occurred as many families were heading to church to celebrate Palm Sunday.