Chinese leader Xi Jinping was in Moscow on a state visit ahead of the big celebrations in the Kremlin marking Victory Day. Meanwhile, Ukraine accused the Russian army of launching air strikes on its territory just hours after the start of a supposed ceasefire, AFP reported.

More than 20 foreign leaders are in Russia to attend a major military parade on May 9 marking 80 years since Nazi Germany's defeat in World War II, three years after the start of Russia's offensive in Ukraine.

During a meeting in the Kremlin, Putin told Xi: "Together with our Chinese friends, we firmly stand guard over historical truth, defend the memory of the events of the war years, and oppose contemporary manifestations of neo-Nazism and militarism."

Russian society has experienced unprecedented militarization during the conflict in Ukraine, and the Kremlin strictly controls the memory of World War II.

Putin said his offensive against Ukraine was aimed at "denazifying" the country, which Kiev called "incomprehensible."

Russia has seized large swathes of Ukrainian territory and destroyed towns and villages in the east of the country with daily bombardments, forcing millions of people to flee their homes.

Xi told Putin that Beijing stands with Russia in the face of "hegemonic bullying," a reference to the two countries' anti-American stance.

"In the face of international opposition to unilateralism and hegemonic bullying, China will work with Russia to shoulder the special responsibilities of major world powers," Xi said.

Before the meeting, Putin called Xi a "dear friend," while he referred to the Kremlin leader as an "old friend."

Putin ordered his army to stop firing on Ukraine for three days to mark the May 9 holiday, an order that took effect at midnight on May 8.

But Ukraine, which dismissed the truce as a theatrical stunt and never said it would observe it, said Russia had violated its own order just hours later.

Ukrainian authorities said Moscow had carried out air strikes on the northeastern region of Sumy overnight.

"During the night, the enemy intensified tactical air strikes using guided air bombs in the Sumy region," the Ukrainian air force said.

However, as of 8:00 a.m., "no missile strikes or attacking drones have been registered in Ukrainian airspace," it added.

Ukrainian President Volodymyr Zelensky repeated his call for an unconditional 30-day complete ceasefire, a proposal made by the US that he had accepted earlier but which was rejected by Putin.

Zelensky condemned the World War II celebrations in Moscow as a "parade of cynicism" and renewed calls for support against Russia.

"Just like 80 years ago, when it finally became clear to everyone: evil cannot be appeased. We must fight it. Together. Resolutely. With force. With pressure," he wrote on social media.

Ukrainian drones caused chaos in transport across Russia this week, closing dozens of airports and forcing hundreds of flights to be canceled or rerouted.

US President Donald Trump has been trying to end Moscow's attacks on Ukraine since taking office in January, but has failed to ease tensions between the enemies.

The White House is increasingly frustrated by the lack of progress, and on May 7, Vice President Mike Pence called on both sides to start direct talks. | BGNES