Censor.NET reports referring to RIA Novosti quoting Peskov as telling journalists on Thursday.
"The fact is no official letter came to the presidential administration. No such document was registered with the presidential administration," Peskov said.
He refused to comment on the information that late Russian envoy to U.N. Vitaly Churkin, speaking at a Security Council meeting, mentioned the existence of this letter and said he was authorized to report the fact.
"I know nothing about this. I can only speak about the situation we have de facto and de jure, that is, what I have already mentioned," the spokesman said.
March 4, 2014, Churkin told the U.N. Security Council about the request of ousted Ukrainian President Yanukovych to send troops to Ukraine.
He read out the letter and confirmed its authenticity.
The military prosecutor's office of Ukraine obtained an official photocopy of the letter from the U.N.
Censor.NET published this historical document.
"As lawfully elected president of Ukraine, I declare that events on the Maidan, the illegal seizure of power in Kyiv have put Ukraine on the threshold of a civil war. The country has plunged into chaos and anarchy. The life, security and rights of people, especially in the southeast and Crimea, are in jeopardy. The country is in the grip of outright terror and violence driven by the West. People are persecuted on political and language grounds.
"In this context, I appeal to the President of Russia Vladimir V. Putin to use the armed forces of the Russian Federation to re-establish the rule of law, peace, order, stability and to protect the people of Ukraine," reads the letter signed by Yanukovych.