The Strategic Rocket Forces announced today that two regiments of RS-24 Yars missiles began combat duty in Novosibirsk and Nizhniy Tagil divisions on December 25, 2013. It's interesting that the Rocket Forces representative was quoted as saying that the missiles began "experimental combat duty". This is a bit strange for a missile that has been in service from some time.
These are apparently the 15 Yars missiles that were expected to enter service by the end of the year. In an earlier announcement, the Rocket Forces said that the Nizhniy Tagil regiment is incomplete - right now it has only six ICBMs.