* First rate increase in more than a year
* Central bank focus shifts to inflation from growth
* Tightening shows confidence banking system more stable
(Adds analysts comment, quotes)
By Chijioke Ohuocha
ABUJA, Sept 21 (Reuters) - Nigeria's central bank unexpectedly raised its benchmark lending rate by 25 basis points on Tuesday, wrong-footing analysts as it switched its attention from boosting growth to battling inflation.
Central bank governor Lamido Sanusi has tended to put economic growth in Africa's biggest oil producer ahead of keeping a lid on price rises, particularly after a near collapse of the banking system last year.
However, Sanusi said reforms introduced since he bailed out nine banks a year ago meant there was now leeway for monetary tightening, raising the benchmark interest rate to 6.25 percent from 6.0 percent in the first hike in more than a year.
"The committee is satisfied that sufficient progress has been made in banking sector reforms to mitigate the risk of monetary tightening to financial institutions," he told a news conference in the capital, Abuja.
He also narrowed the interest rate lending and deposit corridor for commercial banks that sits either side of the bank's benchmark level by lifting the deposit rate to 3 percent below the benchmark from 5 percent previously.
Analysts said the two moves -- effectively a raising of official deposit and lending rates to 3.25 and 8.25 percent respectively -- showed resolve to tame inflation that quickened to 13.7 percent year-on-year in August from 13.0 percent the previous month.
A government spending splurge ahead of January elections is likely to keep upward pressure on inflation, which has also risen this year due to an official data revision in August.
"It signals a decisiveness on the part of the authorities to tackle any developing inflation threat stemming from the surge in spending," said Razia Khan, head of Africa research at Standard Chartered in London.
"It also reflects a degree of confidence that the banking sector is over the worst. A year ago, the Central Bank of Nigeria might not have had the luxury of this policy option. Nigeria is now recovering and putting the crisis behind it."
Nigerian markets were closed at the time the rate move was announced, delaying reaction until Wednesday. Analysts said the naira currency should get a boost, while money market rates and treasury bill yields were almost certain to rise.
"Overall, this means short-dated rates will incrementally catch up with long-dated bond yields," said Samir Gadio, an emerging markets strategist at Standard Bank in London.
QUESTIONABLE IMPACT
Despite the central bank's low benchmark rate over the last year, banks have been reluctant to lower commercial lending costs, hampering growth in one of the continent's most important economies.
Much of their concern stems from the banking crisis, although the establishment of the Asset Management Corporation of Nigeria (AMCON), a "bad bank" that will soak up the crisis' bad loan hangover, should help loosen credit markets.
Some analysts questioned whether Tuesday's modest tightening would make a dent on prices, especially given the extra liquidity that is likely to follow AMCON's inception.
"It's probably more of a symbolic thing to say they haven't completely dropped the ball in respect to inflation," said Alan Cameron, regional analyst at Business Monitor International.
"I'm almost certain it won't have a real material impact on the trajectory of inflation."
Sanusi gave no update on the progress of bidding for the rescued banks, or the establishment of AMCON.
He also forecast growth for this year of 7.78 percent, broadly in line with previous projections, and said the near-term outlook for the naira currency was stable.
(Writing by Ed Cropley; Editing by John Stonestreet, Ron Askew)