Chinese President Xi Jinping and his Russian counterpart Vladimir Putin hailed their bilateral ties as "a stabilizing force in a chaotic world" as they met in Beijing on Thursday.
Putin began a two-day trip to the country, seeking greater Chinese support for his war effort in Ukraine.
It is Putin's first trip abroad since his March reelection and the second in just over six months to China, an economic lifeline for Russia after the West hit it with unprecedented sanctions over its military offensive in Ukraine.
Putin was greeted by Xi at a grand welcoming ceremony outside Beijing's Great Hall of the People, footage by state broadcaster CCTV showed.
In a meeting, Xi then told his "old friend" Putin that China-Russia relations were "conducive to peace."
"China is ready to work with Russia to ... uphold fairness and justice in the world," Xi added.
Putin, in turn, told Xi the two countries' relations were "stabilizing factors in the international arena."
"Relations between Russia and China are not opportunistic and not directed against anyone," Putin said, according to a Kremlin readout.
"Together, we uphold the principles of justice and a democratic world order that reflects multipolar realities and is based on international law," he added.
Following closed-door meetings, the two leaders signed a joint statement on deepening their countries' "comprehensive strategic partnership," state news agency Xinhua said.
The Russian leader's arrival came hours after he hailed his country's troops for advancing on "all fronts" on the battlefield in Ukraine, following a major new ground assault.
The Kremlin said Russia and China had agreed to oppose "further escalation" of the conflict in Ukraine on Thursday.
"The parties note the need to stop any steps that contribute to the prolongation of hostilities," the Kremlin's readout of their joint statement said.
China has dismissed claims it is aiding Russia's war in Ukraine and insisted that the West is exacerbating the conflict by sending arms to Ukraine.
Xi has also rebuffed Western criticism of his country's close ties with Moscow. But their economic partnership has come under close scrutiny from the West in recent months.
U.S. Secretary of State Antony Blinken warned China's support for Russia's "brutal war of aggression" in Ukraine had helped Russia ramp up production of rockets, drones and tanks – while stopping short of direct arms exports.
China claims to be a neutral party in the Ukraine conflict, which it has never condemned and in which it has sought to frame itself as a mediator.
And in a statement to media following talks with Putin, Xi said the two sides agreed on the need for a "political solution" to resolving the war.
"China's position on this issue has always been clear," Xi said in footage broadcast by Russian TV.
That position included "respecting the sovereignty and territorial integrity of all countries" as well as "respecting the reasonable security concerns of all sides," the Chinese leader added.
The remarks echo a paper issued by Beijing last year, which Western countries said could enable Russia to hold much of the territory it has seized in Ukraine.
China also "looks forward to the early restoration of peace and stability on the European continent," Xi said, promising Beijing would "continue to play a constructive role to that end."
Putin in response said he was "grateful" to Beijing for its efforts to help resolve the conflict.
He also referenced Beijing's complaints about growing security cooperation between the United States and its allies in Asia, warning of "harmful" military alliances in the region.
On Thursday afternoon, the Russian leader met Premier Li Qiang – China's No. 2 official – who said Beijing was willing to "continue to deepen cooperation in various fields."
Putin and Xi then attended a ceremony celebrating 75 years of diplomatic relations between Moscow and Beijing, Xinhua said.
China-Russia trade has boomed since the Ukraine invasion and hit $240 billion in 2023, according to Chinese customs figures.
But 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.
An executive order by President Joe Biden in December permits secondary sanctions on foreign banks that deal with Russia's war machine, allowing the U.S. Treasury to cut them out of the dollar-led global financial system.
That, coupled with recent efforts to rebuild fractured ties with the United States, may make Beijing reluctant to openly push more cooperation with Russia – despite what Moscow may want, analysts say.
Putin's post-election trip to Beijing echoes Xi's own visit to Russia after his reanointing as leader last year.
The Russian leader is due to travel to the northeastern city of Harbin for a trade and investment expo on Friday.
