"It was the Iranian authorities' treatment of demonstrators during the Christmas week that made me realize I couldn't continue," public broadcaster NRK quoted Mohammed Reza Heydari as saying.
NRK, which said it had spoken to Heydari, presented his quotes in text rather than audio or video form.
Heydari, who NRK said has served as a consul at the embassy for the last three years, was not reachable for comment.
A friend of Heydari who was contacted by Reuters in Oslo said the diplomat remains in Norway but was not willing to make further statements for the time being.
Iran's Foreign Ministry spokesman Ramin Mehmanparast told Reuters: "The report is baseless. A diplomat returns to the country when his mission is finished in another country."
"Sometimes they stay longer in the country where they served as diplomats for various reasons, including waiting for the end of school semesters of their children," Mehmanparast added.
In the bloodiest unrest since the aftermath of a disputed June presidential poll, eight people were killed on December 27 and over 40 reformist figures, including four advisers to opposition leader Mirhossein Mousavi, have been arrested since then.
The opposition says the vote was rigged to secure President Mahmoud Ahmadinejad's re-election. The authorities deny the accusations, which they say were part of a Western-orchestrated plot to overthrow the Islamic system.
On Tuesday Iran's interior minister warned opposition activists they risk execution if they continue anti-government demonstrations.
Norway's foreign ministry said it was aware of the media reports but that nobody had contacted them about such a case. Norway's Immigration Directorate said it does not discuss any individual cases when asked if Heydari was seeking asylum as some media reports suggested.
Norway has a relatively liberal asylum policy, attracting more and more people from third world countries such as Afghanistan and Somalia in past years. The number of asylum seekers doubled to more than 14,000 in 2008, the last full year for which data is available, including 720 people from Iran.
(Reporting by Oslo and Tehran newsrooms; Editing by Noah Barkin)