Russian currency tumbling after a period of low oil prices

The Russian rouble has hit a low after its central bank allowed the currency to devalue for the twelfth time - including nine falls this month.

It fell to 41.6 against the euro - an all time low - and to 29.3 against the dollar, the lowest level since 2005.

The currency has lost more than 20% of its value against the dollar - largely due to the slumping price of oil on which Russia's economy heavily relies.

The Kremlin has been using reserves to try and support the currency.

However concern that Russia is pumping too much cash into supporting the rouble prompted ratings agency Standard and Poor's to cut the country's credit rating earlier this month for the first time in nine years.

Russia's central bank, which sets the official exchange rates, does not normally allow the currency to lose more than 1% percent of its value in one day against the basket of currencies.

But it has gradually been devaluing the rouble by allowing deeper falls, with it sliding 1.5% on Monday.

Oil revenues have been the main driver of the boom enjoyed by the Russian economy in recent years.

But the sharp declines in the price of crude oil means Russia is facing economic challenges.

The central bank is prepared to continue to defend the rouble in order to avoid a repeat of the 1998 financial crisis, when Russians rushed to withdraw their savings as the currency plummeted.

The Kremlin has warned that the global economic slowdown is continuing to take its toll - predicting that the number of people registered as unemployed would rise to about 2.2 million by the end of 2009, from the current level of 1.5 million.