Russian President Vladimir Putin and Chinese leader Xi Jinping were due to hold further talks on Tuesday amid Western criticism that Xi's visit was giving a boost to Moscow as it struggles to make ground in its year-long war on Ukraine.
The two men spoke for more than four hours on Monday and enjoyed a state dinner at the Kremlin, warmly praising each other as a "dear friend".
While China has sought to cast itself as a potential peace-maker in the Ukraine conflict, the visit also underlined an ever-closer relationship between Moscow and Beijing and was criticised by Washington as providing "diplomatic cover" for Putin.
By contrast, Xi may only speak to Ukrainian President Volodymyr Zelenskiy by telephone.
"We are waiting for confirmation," Ukraine's Deputy Prime Minister Iryna Vereshchuk told Italian newspaper Corriere della Sera. "That would be an important move. They have things to say to each other."
On the battlefields in Ukraine, Russia kept up air raids as well as missile and rocket strikes over a wide area in the east, the Ukrainian military said.
Ukraine said Russia's main aim was to reach the borders of Donetsk and Luhansk regions in the Donbas, large areas of which are already under Russian control.
Russian forces had attacked once again in the city Bakhmut – site of the longest and bloodiest battle of the war – and other targets but had been repelled, it said.
"The occupiers are not stopping their assault on the city of Bakhmut," it said.
Ukraine also said on Tuesday an explosion in Dzhankoi city, in the north of the Russian-occupied Crimea peninsula, destroyed Russian Kalibr-KN cruise missiles as they were being transported by rail.
The defence ministry's intelligence directorate said the missiles were designed to be fired from ships in Russia's Black Sea fleet. It stopped short of claiming responsibility for the blast.
Moscow has been publicly promoting plans for a visit by Xi, its most powerful ally in the face of Western opposition to the war, for months. Xi has sought to portray Beijing as a peacemaker in Ukraine even as he deepens economic ties with Moscow.
Putin told Xi he viewed China's proposals for resolution of the Ukraine conflict with respect. Xi, for his part, praised Putin.
The Chinese proposal has been largely dismissed in the West as a ploy to buy Putin time to regroup his forces and solidify his grip on occupied land. Ukrainian and Western officials fear any ceasefire would merely freeze the front lines, handing Russia an advantage as it struggles to make headway following a serious of setbacks since launching its invasion in February last year.
White House spokesman John Kirby said Xi should use his influence to press Putin to withdraw troops from Ukraine.
The timing of Xi's visit was also a boost to Putin as it came just days after the International Criminal Court (ICC) issued an arrest warrant for the Russian president accusing him of war crimes for deporting children from Ukraine.
Denying the charges, Moscow said it has taken in orphans to protect them. Beijing said the warrant reflected double standards.
U.S. Secretary of State Antony Blinken said Xi's visit suggested that "China feels no responsibility to hold the Kremlin accountable for the atrocities committed in Ukraine".
"Instead of even condemning them, it would rather provide diplomatic cover for Russia to continue to commit those grave crimes," Blinken said.
Foreign policy analysts said while Putin would be looking for strong support from Xi over Ukraine, they doubted his Moscow visit would result in any military backing.
Washington has said in recent weeks it fears China might arm Russia, a plan Beijing has denied.
Kyiv, which says the war cannot end until Russia pulls out its troops, cautiously welcomed Beijing's peace proposal when it was announced last month. Zelenskiy has also said that China arming Russia could lead to World War Three.
Japanese PM heads to Kyiv
While Putin hosted the Chinese president, Japanese broadcaster NHK showed Japan's Prime Minister Fumio Kishida boarding a train at a Polish border town bound for Kyiv, to deliver a message of solidarity and support for Ukraine.
Kishida was set to meet with Zelenskiy, Japan said.
Several European Union countries agreed in Brussels on Monday to jointly buy 1 million rounds of 155 mm artillery shells for Ukraine. Both sides fire thousands of rounds per day in the war of attrition.
The United States announced its latest military aid package, worth $350 million, including more ammunition for HIMARS rocket launchers, howitzers and Bradley Infantry Fighting Vehicles, plus HARM missiles, anti-tank weapons and river boats.