(Recasts; adds comment from analysts)
By Peter Murphy and Nelson Bocanegra
BOGOTA, April 25 (Reuters) - Colombia's central bank on Friday unexpectedly raised the benchmark lending rate for the first time in more than two years, as policymakers sought to ward off inflationary pressures as economic growth gathers pace.
The bank's seven-member board increased the lending rate a quarter-percentage point to 3.50 percent, surprising investors who had expected it to hold rates steady for a 13th consecutive month. The last time borrowing costs were increased was February 2012.
The decision was not unanimous.
Colombia's benchmark interest rate had been held steady at 3.25 percent since March 2013, after a run of cuts that totaled 200 basis points. The bank was able to maintain the rate at that level as inflation remained below the mid-point of its 2 percent to 4 percent target range.
"The increase surprised most of the market," said Daniel Velandia, head Colombia analyst at Bogota-based brokerage Credicorp Capital, who had expected the first rate hike in May.
"The bank's anticipating that it would have had to increase the rate more rapidly (had it waited longer), but I am not sure this means we will have consecutive rate increases each month. It all depends on inflation," he said. "The statement gave a lot of weight to inflation. Inflation will be the guide."
Finance Minister Mauricio Cardenas, who represents the government on the board, said the decision to increase borrowing costs was based on accelerating economic activity which has been bolstered by the long period of comparatively low interest rates.
He also said the time had come for a period of more normal interest rates for the Andean country's economy.
The central bank maintained its 2014 forecast range for economic growth of 3.3 percent to 5.3 percent with 4.3 percent the most likely figure.
Cardenas also said J.P. Morgan's decision in March to increase the weighting of Colombia's sovereign debt in its indexes may not have as big an impact on the currency as analysts have speculated.
The peso strengthened sharply in the days following that announcement as a surge of foreign cash flowed in to buy bonds and stocks.
Colombia's pace of inflation has begun to quicken after last year falling to its lowest since 1955. Annual consumer prices rose 2.51 percent in March and were up 0.39 percent from the prior month.
"The macro signs point to a growth dynamic that looks to be strengthening with the latest indicators and inflation that expectations show are moving toward the target," said Camilo Perez, chief analyst at Banco de Bogota. (Additional reporting by Helen Murphy; editing by G Crosse and; Bernard Orr)