Russian leader Vladimir Putin was in the northeastern city of Harbin on Friday, the final day of a visit aiming to promote crucial trade with China and win greater support for his war effort in Ukraine.

Putin arrived Thursday on his first trip abroad since his March re-election, meeting President Xi Jinping for talks in which the leaders framed their nations' ties as a stabilising force in a chaotic world.

China and Russia's strategic partnership has only grown closer since the invasion of Ukraine, and Beijing has rebuffed Western claims that it is aiding Moscow's war effort.

China has also offered a critical lifeline to Russia's isolated economy, with trade booming since the invasion and hitting $240 billion in 2023, according to Chinese customs figures.

Putin's trip to Harbin is part of efforts to enhance that economic relationship.

The city, near the border with Russia, has long served as a key hub for cross-border trade and cultural exchange.

Speaking at the opening ceremony of a Russia-China trade expo on Friday, Putin hailed energy ties between the two countries and promised to "strengthen" them.

"Russia is ready and able to continuously power the Chinese economy, businesses, cities and towns with affordable and environmentally clean energy," he said.

"As the world is on the threshold of the next technological revolution, we are determined to consistently deepen bilateral cooperation in the field of high technologies and innovations."

Moscow's state news agency TASS said Putin was accompanied by Han Zheng, China's vice president.

- Western criticism -

Putin's visit comes a week after a major new ground assault in Ukraine, Moscow's biggest advance in 18 months.

Thousands of Russian troops stormed the border into Ukraine's northeast on May 10, seizing over 200 square kilometres (77 square miles) of land.

At a news conference on Friday, Putin said the move had been made to stop cross-border shelling, but added there were no current plans to capture Kharkiv city.

"This is their fault because they have shelled and continue to shell residential neighbourhoods in border areas," Putin told reporters.

"I said publicly that if this continues, we will be forced to create a security zone."

Putin said he and Xi had discussed the conflict, noting that he believed China "is sincerely seeking to resolve this problem".

Western countries meanwhile have been mounting pressure on Beijing to cut off support for Russia's economy.

After Washington vowed to go after financial institutions that facilitate Moscow, Chinese exports to Russia dipped in March and April, down from a surge early in the year.

But Xi said in a statement following talks with Putin on Thursday that the two sides agreed on the need for a "political solution" to resolving the war.

The two men later ditched their ties for a less formal meeting over tea at the palatial Zhongnanhai leadership compound.

China's state broadcaster aired footage of Xi embracing Putin following their talks, which saw the Chinese leader express support for an "international peace conference recognized by Russia and Ukraine".

There are no indications Moscow and Kyiv are prepared to engage in direct talks, which Ukraine says would only be used by Russia to buy time to prepare for a new assault.

Hours after Xi and Putin met, US State Department spokesman Vedant Patel said that China couldn't "have its cake and eat it too" with regard to the West and Moscow.

"It can't have it both ways and want to have (better) relationships with Europe and other countries while simultaneously continuing to fuel the biggest threat to European security in a long time," Patel said, referring to Russia's invasion of Ukraine.