A Russian drone attack on a school near Kyiv killed at least four people before Chinese leader Xi Jinping left Moscow on Wednesday at the close of a summit with President Vladimir Putin.

Xi called each other "dear friend" and hailed a "new era" in their nations' ties following two days of talks marked by pomp and a display of unity against the West.

But there was no apparent breakthrough on the war in Ukraine, despite Beijing touting a "visit for peace", and few concrete economic proposals were signed.

Both eager to curb Western dominance, Putin and Xi expressed concern about NATO expansion in Asia and agreed to deepen a partnership which has grown closer since Putin invaded Ukraine a year ago.

Xi's plane left Moscow's Vnukovo airport on Wednesday after being seen off by an honour guard, capping a visit that was seen as a boost for the internationally-isolated Russian leader.

But in Ukraine, at least four people were killed and others wounded in a drone attack that hit a school in the Kyiv region late Tuesday, officials said Wednesday.

Ukraine's air force said Russia attacked Ukraine with 21 "Iranian-made" drones overnight, and 16 were shot down.

During the Moscow summit Putin said he was open to talks on Ukraine and praised Beijing's 12-point position paper on the conflict, which includes a call for dialogue and respect for all countries' territorial sovereignty.

After talks with Xi, Putin said that "many of the provisions" of China's initiative can form the basis of a peace settlement for Ukraine when Kyiv and the West are ready for it.

"However, so far we have not seen such readiness on their part," he added.

Ukrainian President Volodymyr Zelensky said Kyiv had invited China to talks, and was waiting for an answer from Beijing.

The United States, however, said it does not see China as capable of being an impartial mediator -- Washington's most direct criticism yet of Beijing's aim to be a middleman in efforts to end the conflict.

On Wednesday, the Kremlin said it was not surprised by the West's "hostile" reaction to the summit.

'Unlimited possibilities'

Moscow and Beijing have over the past years ramped up cooperation, both driven by a desire to counterbalance the US-dominated international order.

The Chinese leader's Moscow visit has been viewed as a coup for Putin, who is subject to an International Criminal Court warrant over accusations of unlawfully deporting Ukrainian children.

"I am sure that Russian-Chinese cooperation has truly unlimited possibilities and prospects," Putin said at a state dinner following the talks, where he toasted the "prosperity" of Russian and Chinese people.

He also gushed over the "special nature" of the relationship between the two countries.

On the second day of his visit to Moscow, Xi said ties with Russia were "entering a new era".

Putin called the talks "meaningful and frank" and said that Russia, which has been largely cut out of European markets because of sanctions, would be able to meet China's "growing demand" for energy.

Putin said the two countries had reached an agreement on the Power of Siberia 2 gas pipeline, which will send Russian natural gas to China via Mongolia.

Despite Russia's keen interest, analysts have warned that there will be limits to the relationship.

US 'undermining' global security

In a joint statement, the two leaders took aim at the West, accusing the United States of "undermining" global security, and expressed "great concern" over NATO's growing presence in Asia.

China and Russia have often worked in lockstep at the UN Security Council, using their veto power as permanent council members to counter the West.

Russia's assault on Ukraine has also deepened fears among Western powers that China could one day try to take control of the self-ruled island of Taiwan, which Beijing sees as part of its territory.

China has sought to portray itself as a neutral party in the Ukraine conflict, but Washington has said Beijing's moves could be a "stalling tactic" to help Moscow.

The United States has also accused Beijing of mulling arms exports to Moscow, claims China has denied.

Japan PM in Kyiv 

Xi's trip coincided with a surprise visit to Kyiv by Japanese Prime Minister Fumio Kishida, who on Tuesday also visited Bucha, a town where Russian forces were accused of committing atrocities last year.

"Our talks with Mr Kishida were quite productive," said Zelensky.

"I also heard a very concrete willingness of Japan to work together with us to even more actively mobilise the world for international order, to protect against aggression, to protect against Russian terror."

Kishida, the last Group of Seven leaders to visit the country, had come under increasing pressure to make the trip, as Japan hosts the group's summit this May.

Zelensky confirmed on Tuesday he would participate in the G7 summit via video link.