Move is latest in line of retaliatory actions by Moscow since a Russian Su-24 fighter jet was shot down over Turkey on TuesdayRussia will introduce a visa regime for Turkish citizens as part of a range of measures to retaliate for the Su-24 fighter jet downed by the Turkish air force on Tuesday.The foreign minister, Sergei Lavrov, announced the latest move on Friday, saying it would come into force from 1 January.