While Foreign Minister Sergei Lavrov implies Ukraine is “undemocratic” for voicing suspicions about Russia – which not only seized and annexed Ukraine's Crimea Peninsula in March 2014 but has backed separatists in eastern Ukraine – Kyiv has valid grounds to implicate Russia in the murder of a Russian MP who fled to Ukraine fearing for his life, and who told reporters of threats made against him.
Voronenkov was a key witness in Ukraine’s treason case against deposed President Viktor Yanukovych. In January 2017, Ukrainian Prosecutor General Yuriy Lutsenko announced that Voronenkov had given testimony about two letters written by Yanukovych in February 2014, one of which was registered with the UN Security Council by Russia on behalf of Yanukovych by the late Ambassador Vitaly Churkin, in which Yanukovych requested Russian troops to put down the Maidan demonstrations 
Both Yanukovych and the Kremlin denied that any formal letter had been submitted despite the official record at the UN showing otherwise.
The independent Russian news site Novaya Gazeta has also written about Voronenkov’s business dealings which involve an offshore account that came to light in the Panama Papers. It has also covered Voronenkov’s claims that agents of the Federal Security Service (FSB), which he allegedly exposed as involved in contraband, had a vendetta against him. These circumstances could also give grounds for suspecting a murderer from Russia.
As for the explosion of the ammunition depot in the eastern Ukrainian town of Balakliya in which one person was killed and a half dozen injured, the Ukrainian military called it an “act of sabotage." Some Ukrainian military experts have expressed skepticism about the hand of Moscow, as negligence could also be a factor.
But the week following Voronenkov’s murder, there was also a grenade attack on the Polish Consulate in the western Ukrainian city of Lutsk. President Petro Poroshenko and other officials believed this, too, to be the work of Russian or Russian-backed saboteurs because Moscow would have the means and the motive.
Throughout the war in Ukraine, there have been dozens of cases of bombings in Ukraine, such as the February 2015 explosion in Kharkiv that killed 2 and injured 10. Police said the suspect's weapons were provided by Russia.
Stephen Blank, an expert on Russia and currently a Senior Fellow at the American Foreign Policy Council, has outlined Russian measures in Syria and elsewhere in the Middle East as well as Ukraine and the UK (the Litvinenko murder) and describes these as the “actions of a state sponsor of terrorism."
Ultimately, it does not diminish Ukraine’s status as a democracy with a relatively free media if the president and other officials freely voice suspicions that have some validity given the Kremlin’s track record of aggression. Furthermore, even when the Ukrainian prosecutor general has established facts, with credible testimony from Voronenkov, the Russian government scoffed at them.
Throughout the wars in Ukraine and Syria, there have been numerous occasions when overwhelming numbers of facts of atrocities have been established, such as with the shooting down of MH17 or the latest chemical weapons attack and the Kremlin’s strategy has been to float one dubious counter-narrative after another, and distract with attacks on the credibility of accusers.