Russia's ruble has slumped to a three-year low as oil prices keep hurting this oil price-dependent country, according to AP. The ruble went down 0.5 percent to 32.9 rubles against the U.S. dollar in early trading on Thursday. The Russian currency has been declining for seven days and lost some 3.5 percent this week as oil prices went down. The Russian Central Bank, which occasionally intervenes on the market to support the currency, has so far refrained from propping up the ruble. The oil benchmark for July delivery lost 0.1 percent to $87.9 in early trading at the New York Mercantile Exchange. Russian markets posted moderate gains Thursday morning.