A leader of Ukrainian fascist gang Right Sector has been gunned down by police as they tried to arrest him.

Oleksandr Muzychko, better known as Sashko Bily, was a key figure in the street group that formed the most violent and well-organised wing of the anti-government protests.

Police raided a cafe in Rivne in western Ukraine late on Monday night but Muzychko and his far-right co-conspirators opened fire as they tried to escape, local media reported .

Coup-installed Deputy Interior Minister Vladimir Yevdokimov said Muzychko and three other members of his "criminal gang" were arrested but the 54-year-old was dead by the time paramedics got to him.

Born in Perm, Russia, Muzychko was jailed in 1999 for extortion.

Russian authorities had wanted him arrested for torturing and murdering Russian personnel while serving with Chechen warlords in the '90s.

After storming Grozny he "broke the fingers on the hands of army officers, put out eyes, pulled out their nails and teeth with pliers, cut the throats of some of them and shot dead the others," according to one of the Ukrainians he served alongside.

His death came shortly after Russian Foreign Minister Sergei Lavrov met his Ukrainian counterpart Andriy Deshchytsia on the fringes of a nuclear security conference in The Hague.

It was the first meeting between the two countries since Crimea voted to rejoin Russia.

Meanwhile the withdrawal of Ukrainian forces from the Crimea continued.

Defence Minister Igor Tenyukh resigned after saying that 4,300 servicemen and 2,200 family members would be evacuated from Crimea to Ukraine.

It means that about two-thirds of the 18,800 military personnel and their relatives have opted to transfer their allegiance to the Russian Federation.

Mr Tenyukh had previously been criticised for failing to give clear orders to troops in the region.