Ukraine has issued an arrest warrant for ousted president Viktor Yanukovych as the country’s new rulers launched a probe over the government’s “mass murder” of protesters in Kiev.

“An official case for the mass murder of peaceful citizens has been opened. Yanukovich and other people responsible for this have been declared wanted,” acting interior minister Arsen Avakov said in a statement posted on his Facebook account. He said that Yanukovych, who vanished on Saturday, had left a private residence in the town of Balaclava with an aide.

Ukrainian law enforcement agencies said earlier they have no information about the whereabouts of Yanukovych, who reportedly was seen in Sevastopol, a port on Ukraine’s Crimean Peninsula that is the home of Russia’s Black Sea Fleet.

But claims have emerged that he was sneaked onto a Russian warship or plane in Sevastopol to flee possible legal action.

A former senior aide to Russian leader Vladimir Putin said that that “a major operation” was conducted in the port which is also headquarters to the Ukrainian navy.

Former economics advisor Andrey Illarionov claimed the secret evacuation was assisted by Ukraine’s defense minister Pavlo Lebedyev, who remains loyal to Yanukvych, and Russian forces in Sevastopol.

Illarionov said his sources indicated that it “looks like Yanukovich managed to sneak out.”

Opposition lawmaker Volodym Kurennoy said on his Facebook page that he had unconfirmed information that the president had been arrested in Crimea.

However, Ukrainain news portal Liga.net reported that Sevastopol residents saw Yanukovych in the company of Russian marines. The claim could not be independently verified.

The speaker of Ukraine’s parliament assumed the president’s powers on Sunday, but a presidential aide said that Yanukovych plans to stay in power.

Russia said on Sunday it was calling its ambassador to Ukraine back to Moscow for “consultations”, AFP reported.