(Reuters) -Annual inflation in Russia accelerated to 16.70% as of April 1, its highest since March 2015 and up from 15.66% a week earlier, the economy ministry said on Wednesday, as the volatile rouble sent prices soaring amid unprecedented Western sanctions. Inflation in Russia has accelerated sharply in the past few weeks as the rouble’s fall to an all-time low boosted demand for a wide range of goods from food staples to cars on expectations prices will rise even more. Weekly inflation in Russia slowed to 0.99% in the week to April 1 from 1.16% a week earlier, taking the year-to-date increa…