The Russian rouble weakened against the dollar on Friday as demand for foreign currency edged up, with some traders saying that Ukraine’s surprise attack in Russia’s Kursk region was one of the factors. At 0750 GMT the Russian currency was 0.8% lower at 84.35 to the dollar. According to an analysis of the over-the-counter market, the rouble was down 0.1% at 11.89 against the yuan, which has become the most traded foreign currency in Moscow. Russian forces are battling Ukrainian troops for a fourth day after they smashed through the Russian border in the Kursk region in one of the biggest Ukrainian attacks on Russia since the war began in February 2022.