A word for "government by murderers"

Is there a word that describes government by murderers (or just criminals in general) similar to kleptocracy being a government of thieves? I'm looking for something that contains more of this sense than either despotism or tyranny, but would not necessarily be as extreme as a democidal regime of the order of Idi Amin's or that of the Khmer Rouge. I recently heard such a situation described as a "Mafia state", but is there a more appropriate one-word alternative?

You could use cidocracy, as Gibson Burrell has done in his Pandemonium: Towards a Retro-Organization Theory (1997):

In classic Orwellian 'Newspeak', of course, defence means war, the 'Final Solution' meant genocide and 'Lebensraum' meant the Slavic killing fields. What we really face here in the Square of Pandemonium is 'cidocracy'. Certainly the Enlightenment did not create rule by killers ‒ but it made them much more efficient in waging war.

Google Books link

This combines cid-, to kill, with -cracy, rule.

I came across kakistocracy (or cacistocracy, see also kakocracy/cacocracy):

Government under the control of a nation's worst or least-qualified citizens. - wiktionary

According to Google NGrams, this seems in significantly more common usage than thanatocracy, while cidocracy does not appear at all within the Google books english corpus.