As he stepped out of his limousine in the capital Ulaanbaatar, Putin was greeted by his Mongolian counterpart Ukhnaagiin Khurelsukh in front of a row of ceremonial guardsmen on horseback wearing helmets with pointed tops.
The Kremlin leader stooped to kiss a young girl who stepped forward to welcome him in Russian and present him with flowers.
Mongolia is the first country Putin has visited that's a member of the International Criminal Court. (AP PHOTO)
An International Criminal Court (ICC) arrest warrant issued last year against Putin obliges the court's 124 member states, including Mongolia, to arrest the Russian president and transfer him to The Hague for trial if he sets foot on their territory.
Mongolia's failure to act on it was "a heavy blow to the International Criminal Court and the system of criminal law", Ukrainian Foreign Ministry spokesperson Heorhiy Tykhyi said.
"Mongolia has allowed an accused criminal to evade justice, thereby sharing responsibility for the war crimes," he wrote on the Telegram messaging app. Ukraine.
He said he would work with Ukraine's allies to ensure Mongolia felt the consequences.
The United States, which is not a member of the ICC and is keen to develop relations with Mongolia as an important source of rare-earth minerals needed in high-tech applications, was also critical of Ulaanbaatar.
"We don't believe any country should give Putin a platform to promote his war of aggression against Ukraine," State Department spokesperson Matthew Miller told a regular briefing.
"We do expect Mongolia to adhere to its commitment and support for the principles of the UN Charter, including sovereignty and territorial integrity, and convey that those principles must be upheld around the world," he said.
Miller said Washington understood Mongolia's position sandwiched between two larger neighbours, which are China and Russia, but added; "We do think it's important that they continue to support the rule of law around the world."
While the US is not an ICC member, it supported the court's decision to issue an arrest warrant for Putin.
The ICC warrant accuses Putin of illegally deporting hundreds of children from Ukraine. The Kremlin has rejected the accusation, saying it is politically motivated.
Kremlin spokesman Dmitry Peskov said last week that Moscow had no worries about any action in connection with the warrant, as Russia had a "great dialogue" with Mongolia and all aspects of the visit had been discussed in advance.
"Relations with Mongolia are among the priorities of our foreign policy in Asia. They have been brought to a high level of comprehensive strategic partnership," Putin told Khurelsukh.
