The Central Bank spent an estimated $7 billion on Tuesday on establishing a new limit for the ruble after allowing it to weaken beyond a key level it had defended in recent months.

After breaking through its former 30.41 limit against a euro/dollar basket, the ruble weakened as far as 30.79, and analysts said the move underlined the strain intervention has put on national currency reserves.

Some analysts also highlighted the risk that ruble weakness could spread worry among ordinary Russians who remember the country's 1998 financial crisis.

The ruble closed at 30.70, and the Central Bank issued a statement saying it had widened the ruble's trading band by 30 kopeks in each direction "to increase the flexibility of the exchange rate." Previously, the band was seen around 29.25 to 30.41.

Dealers estimated that the Central Bank had sold $7 billion on Tuesday to defend the new mark -- more than it had spent on …