Russia's central bank has raised the upper limit of the floating currency band as the ruble continued its slide amid increased investor fears of a recession in the United States and Europe, traders said on Monday. The regulator moved up the upper end of the ruble value of the bi-currency basket comprising $0.55 and 0.45 euros to 37.50 from 37.35 rubles in an effort to quash the ruble's excessive volatility. Last Friday the upper end of the ruble basket band was moved to 37.35 from 37.20 and the shift implied at least a $5 billion of interventions. On Monday, the Central Bank most likely moved up the upper end of the basket by another 15 kopecks. Right now the basket value remains below this boundary and the Central Bank is managing to keep it within the band," said Sergei Romanchuk, head of the dealing center at Metalloinvest bank. The average-weighted rate of the ruble fell by 27 kopecks against the dollar to 32.34 and by 27 kopecks against the euro to 43.37 as of 15:00 p.m. Moscow time on Monday. The value of the bi-currency basket rose 30 kopecks to 37.44 rubles by 14:55 Moscow time, MICEX data suggested. "The situation on global markets (including raw material markets) remains unstable but investors are beginning to show cautious optimism, linking their hopes with the support of the European financial sector by the European Central Bank. In particular, during the week European parliaments will vote on the enlargement of the financial stability fund and possible a decision will be taken on providing aid to Greece," said Dmitry Kulakov, head of the shares department at Olma investment group. Kulakov also said that the European Central Bank might discuss a possible lowering of its key rate in October. The index of the ruble-denominated MICEX stock exchange increased 2.64 percent to 1,362.29 as of 16:01 Moscow time, while the dollar-denominated RTS stock exchange rose 1.27 percent to 1,332.69.