A reported comment by President Vladimir Putin that Russia could capture Ukraine's capital Kiev within two weeks was taken out of context, Itar-Tass news agency quoted a Kremlin foreign policy aide as saying on Tuesday.
It quoted Yuri Ushakov as saying that whether or not those words were spoken, the quote "was taken out of context and had a totally different meaning".
Italy's La Repubblica reported this week that Putin told European Commission President Jose Manuel Barroso in a telephone conversation: "If I want to, I can take Kiev in two weeks". The comment was reportedly relayed by Barroso to leaders at last weekend's European Union summit.
Ukrainian President Petro Poroshenko accused Russia on Monday of "direct and undisguised aggression" which he said had changed the battlefield balance as Kiev's forces suffered a reverse against pro-Moscow separatists. Moscow denies direct engagement of its troops in the war in Ukraine.
Putin had called on Sunday for immediate negotiations on the "statehood" of southern and eastern Ukraine.
Read MorePutin calls for talks on east Ukraine 'statehood'
Tass quoted Ushakov as criticising Barroso, saying it was "improper" and undiplomatic to relay details of the conversation.
"If this was done, then it seems to me unworthy of a serious political figure," he said.
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