Putin is dangerously close to having to choose between feeding his people or buying weapons if the war with Ukraine continues, a leading Russia expert has warned.

Russia has found that expendable convict-soldiers can clear the way for regular troops, but these tactics come at a massive cost.

Russian ruler Vladimir Putin signed a series of laws that toughened penalties for armed rebellion and crimes against military service and approved a new strategy to counter extremism, which lists the elimination of threats emanating from Ukraine as one of its main tasks.

Ukraine will quadruple gas transmission tariffs for domestic consumers from Jan. 1 to offset the impact of lost revenue following the year-end expiry of the gas transit agreement with Russia, officials said on Monday.

Ukraine's decision to turn off the taps keeping Russian gas flowing via its territory to Europe has already sown trouble in the continent's east, with Moldova declaring a state of emergency and Slovakia threatening Kyiv with retaliation.