"I’m not going to tell you," he said in comments made during the plenary session of Russia’s premier investment forum in St Petersburg on Friday.
While clearly uncomfortable when being asked about his ally’s recent conduct, the Russian president offered a robust defence while reverting to claims of ignorance.
Mr Putin said he knew nothing about the blogger – Roman Protasevich – who the Belarusian president commandeered off a Ryanair flight last month. He also forgot to mention Mr Protasevich’s girlfriend, Sofia Sapega, a Russian citizen, who has been held without charges.
"I don’t want to give you my assessment about what happened," the Russian leader said. "I honestly don’t know. I don’t know Roman Protasevich and don’t want to know him. Let him do what he wants to do. Let him fight with the regime."
Fears are growing that Mr Protasevich is being subjected to serious physical and psychological harm while under Mr Lukashenko’s watch.
A video of a "confession" interview recorded under duress showed wrists with deep flesh wounds suggesting deliberately improper use of handcuffs. On Monday, Mr Lukashenko made a scarcely veiled threat to hand his opponent over for a death penalty trial at the hands of Russian-backed combatants in eastern Ukraine.
Still, Mr Putin insisted the issue was a "domestic Belarusian affair”, and claimed Russia was trying to hold a "neutral position" while the West was "interfering”.
He laughed away suspicions that Russian agents may even have been involved in planning the operation to kidnap Mr Protasevich.
"I saw all these statements made by Nato’s leadership that Russia had taken part, but I want to say this: if Nato is making statements like this, it’s in real danger," he said. "It means people don’t understand the processes involved."
For all his words about national sovereignty, Mr Putin made several unexpected interventions into US domestic politics.
Without a hint of irony, he drew attention to what he said was an excessive clampdown on Trump supporters. Those involved in post-election clashes on Capitol Hill were not rioters, he said, but "Americans with political demands".
"More than 450 people were arrested, and now all face criminal charges," he said. "Rubber bullets can take out your eyes, you know. Tell the victims: there, there, it’s only a democratic bullet."
Mr Putin, who appeared to be in generally accommodating mode ahead of his 16 June summit with Joe Biden in Geneva, said the Kremlin was not, in fact, in direct conflict with the United States.
"We have only one disagreement with them," he said.
"They want to rein in our development. Everything else derives from that."
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