(Adds details, background, rouble, budget, analyst quotes)
By Toni Vorobyova
MOSCOW, Oct 29 (Reuters) - Russian economic growth slowed to a 2-1/2 year low in the third quarter, the country's Economy Ministry estimated on Wednesday as it cut its forecast for the full year in the face of the global credit crunch and falling oil price.
Even as data showed growth picked up to an annual 7.6 percent in September, for the third quarter as a whole it slowed to 7.1 percent year-on-year, the ministry estimated.
That would be its slowest pace since early 2006 and marks a deceleration from 7.5 percent in the April to June period.
"The worsening of the liquidity situation in global financial markets in the late summer-early autumn 2008 has led to increased outflow of capital from Russia," the ministry said.
"From August, the fall of natural resource prices has accelerated, especially for oil. Lower demand, both internally and externally, has led to slower economic growth."
The ministry forecast a further slowdown in growth in the fourth quarter to an annual 6.5 percent, and said the economy would likely expand by 7.3 percent in 2008 as a whole.
That was a downward revision from an earlier forecast of 7.8 percent for 2008 and would be the slowest growth since 2005.
Some analysts are even less optimistic -- Danske Bank has cut its 2008 view to 6.8 percent from 7.0, while Goldman Sachs has slashed its forecast to 6.2 percent from 7.5 percent.
"Both parts of domestic demand - investment and consumption - are likely to slow quite significantly," said Gaelle Blanchard, analyst at Societe Generale in London.
"The consumer is also hurt by inflation which reduces the real income," she added.
The crisis has prompted Russian authorities to switch their focus away from taming inflation, and data on Wednesday showed consumer prices have risen 11.5 percent since the start of the year.
Lower commodity prices are another reason for slowing growth in Russia's resource-dependent economy.
The price of Russia's Urals blend oil has fallen more than 50 percent from its July peaks to around $60 a barrel.
Deputy Finance Minister Dmitry Pankin said on Wednesday that if such a level is maintained, next year's budget -- based on $95 oil -- will still balance, but the 2010 budget would need to be revised or supplemented with reserve funds.
ROUBLE PRESSURE
Russian Finance Minister Alexei Kudrin has said that "the next two months will show the real picture" on growth.
Proof of a sharp slowdown could be an argument for allowing some depreciation of the rouble -- a move which could help Russia's exporters and also stop the huge drain on the country's reserves from currency-supporting interventions.
"Slowing growth and lower oil prices increase the chances of a weaker rouble," said Lars Rasmussen, analyst at Danske Bank.
"But it's a very tricky situation. I do not think they are going to do anything this year, it's way too dangerous for many reasons... That would just increase capital outflows, add to inflationary pressure and thirdly there are big refinancing schemes of external debt in private sector."
Against a euro-dollar basket, the rouble traded around the 30.41 level, which the central bank has been defending by selling tens of billions of dollars since August. (Reporting by Toni Vorobyova; Editing by Victoria Main)