It forecast that real gross domestic product (GDP) would grow by 2.8 percent in 2015 and 2.4 percent in 2016, down from 3.5 percent last year. Oil revenue was seen contributing 24.2 percent to GDP this year, down from 32.6 percent in 2014.

"Risks to the growth outlook are tilted to the downside," the IMF said in Wednesday's report, which followed a visit by its economists to Riyadh in May.

"The main downside risks are the possibility of lower oil prices due either to weaker global demand or increased supply, the possibility that domestic reforms do not generate a growth dividend and create a more diversified and self-sustaining private sector that creates jobs and reduces inequality and an escalation of regional tensions that undermines confidence and investment," it continued.