President of Ukraine Petro Poroshenko told Sky News in an exclusive interview, Censor.NET reports.
Three people died after grenades were thrown during clashes between nationalists and police outside Ukraine's parliament.
It followed a vote to give more powers to the regions, including separatist regions in the east.
Petro Poroshenko told Sky News the killings were inspired by Moscow.
In an exclusive and wide-ranging interview, he insisted that his reform program to bring his country closer to European Union norms and requirements was on track, notably tackling corruption and the planned lifting of immunity for politicians - including himself.
But it is the tsar-like leadership of Vladimir Putin that he says is a threat not only to his country but to wider European and global security - pointing out that even the UK regularly has Russian military aircraft testing its air space.
Poroshenko said that Russia had become "unpredictable" but he did not feel vulnerable, even though "this is one of the most difficult presidencies in the whole world".
His claim that Russia may have been behind the grenade attack on the police will gain credence among conspiracy theorists and some military theorists. Moscow has pioneered what is now known as "hybrid warfare" - the use of covert operators to foment instability.
Ukraine's president said he was proud of his country's ability to hold back the Russians and rebels given that a year ago he was told that "half your army is corrupt and the other 50% are Russian agents" by NATO and other western supporters who have now begun training his forces.
Poroshenko was adamant that he would also bring reforms to the country's notoriously corrupt economy, insisting that constitutional reforms lifting immunity from parliamentarians and the judiciary would be driven on - even in the face of the very politicians who may soon come under investigation by newly foreign trained anti-corruption detectives.
"War is not an excuse to stop reforms," he said.
His hopes are most pinned on a cease-fire agreement that was signed many months ago but has only seen respect in the last six days, with no serious casualties reported from the front line.
"The only reason that the Russians came to Minsk and are prepared to negotiate at all was as a result of economic sanctions imposed by the outside world," he said, insisting that Ukraine did not need troops but it would continue to need the support of the international community.
He is forging ahead with plans to move yet further away from the Kremlin's influence and closer to the European Union - precisely the policy that has so angered Vladimir Putin, the Russian president. So it is hard to see an end to Ukraine's conflict any time soon.
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