Major Russian and Chinese companies, meanwhile, signed cooperation agreements.

Chinese President Xi Jinping began a three-day visit to "best friend" Vladimir Putin on Wednesday with a touch of panda diplomacy and a raft of new Russian-Chinese business contracts.

The leaders praised their countries' ties during talks at the Kremlin, as Russia and China seek to shore up cooperation amid shared tensions with the US.

"President Putin is for me a best friend," President Xi told journalists during a joint statement following the meeting.

"We decided that we would raise our bilateral relations to a new, higher level - increasing our mutual support and assistance, and promote our relations in a new era," he said, in remarks translated into Russian.

Russian President Putin thanked his Chinese counterpart for an earlier loan of two pandas that are being housed at the Moscow Zoo.

"This is a sign of a special respect, of a special trust in Russia," he said. "When we speak about pandas, a smile always appears on our face."

The two men signed a joint statement on the development of comprehensive partnership and strategic cooperation.

Major Russian and Chinese companies, meanwhile, signed cooperation agreements.

China's Alibaba, Russian mobile phone operator Megafon, internet group Mail.ru and the Russian sovereign investment fund RDIF closed a deal on a joint e-commerce venture.

Mail.ru head Boris Dobrodeyev said in a statement that the new company AliExpress Russia would become the "undisputed leader in Russian e-commerce".

Russian telecoms company MTS and Chinese Huawei also signed a memorandum of understanding, while Russia's Novatek and Gazprombank signed an agreement with Sinopec to market gas in China.

'Most important economic partner'

The trip comes five years after Moscow's annexation of Ukraine's Crimea peninsula led to a serious rift with its Western partners and subsequent turn toward its neighbour to the east.

"In recent years, thanks to your direct participation, the relationship between Russia and China has reached an unprecedentedly high level," Mr Putin told Xi on Wednesday.

Xi, who was received with full honours when he arrived at Moscow's Vnukovo airport in the afternoon, was set to attend a performance at the Bolshoi Theatre in the evening.

He will later travel to the former imperial capital of Saint Petersburg for an economic forum hosted by Putin on Thursday and Friday.

China and Russia "have strong political mutual trust, and support each other firmly on issues concerning each other's core interests and major concerns," Xi said during an interview with Russian media ahead of the visit.

The partnership is yielding increasing trade, which grew by 25 per cent in 2018 to hit a record $108 billion (96 billion euros), according to the Kremlin.

Putin's foreign policy aide, Yuri Ushakov, earlier called China "Russia's most important economic partner".

Russia's 'pivot' paying off

Russia may have had unrealistic expectations from its pivot to the east following Western sanctions over Ukraine, said Alexander Gabuev, who heads the Asia programme at the Carnegie Moscow Centre.

Nevertheless, China's share in Russian foreign trade has nearly doubled since then, he added.

"The pivot really is happening," he said.

"Despite all the difficulties, China became a significant creditor and rather significant investor" in Russia at a time when many other investors preferred to pack their bags.

Cooperation with China is seen by Moscow as "the lesser of two evils" to stimulate economic growth, Gabuev said - the alternative being deep internal reforms and reconciliation with the West.

Politically, the two countries seem consistently aligned and often vote in unison as permanent members of the UN Security Council.

Presidential advisor Ushakov said "the positions of Russia and China are very close or coincide completely on most international issues", including the North Korean nuclear programme, the Venezuelan crisis and the Iran nuclear deal.

Moscow's relations with Washington have been at a post-Cold War low for some time, and Beijing is locked in a trade war with the US.

After Washington criticised its rights record, Beijing issued a travel warning to Chinese nationals Tuesday about crime and police harassment in the US.