"This will have spillover effects on the wider economy and unemployment may edge up ahead," it added.
Read MoreWhy rich Norway can't afford to be complacent
Olsen told CNBC there was a "50-50" chance of another interest rate cut during the first half of next year. The Norwegian central bank was an early adopter of "forward guidance."
Norway's growth prospects, already weighed down by falling oil investments, took a turn for the worse in recent months as oil prices tumbled 40 percent over the past six months and investments in the offshore petroleum sector could fall by 15 to 20 percent next year.
Olsen forecast oil prices would rebound, but not up to the $100 level seen before this past September.
The central bank now sees economic growth on mainland Norway, excluding the offshore oil and gas sector, at 1.5 percent next year, below earlier forecasts for 2.25 percent.
'Immediate' inflation hit from oil
Also Thursday, the Swiss National Bank opted to keep its interest rates unchanged. The bank held its target range for three-month Libor at 0.00-0.25 percent, as analysts polled by Reuters had expected.
In conversation with CNBC, Swiss Central Bank Chairman Thomas Jordan said falling oil prices had had "immediate impact" on inflation in Switzerland—which unlike Norway, is not an oil producer.
"It is extremely important that inflation expectations remain in positive territory," he told CNBC on Thursday.
Like its neighbors in the euro zone, Switzerland is grappling with disinflation and deflationary pressures. Consumer price inflation in Switzerland was flat for a second consecutive month in November.