Alexandra Joner, a 19-year-old Norwegian-Cuban woman, alleged that the diplomat - the wife of the Cuban ambassador - had attacked her on the sidelines of the pro-democracy demonstration on Saturday.
"She stepped in front of me. I didn't say anything. But then she started insulting me in Spanish. She took pictures of me, and I asked her to stop," Joner, who was filming the event, told the TV2 News Channel.
"I put my hand in front of the camera and then she bit me," Joner added.
The incident appeared to be partially corroborated by the film Joner was shooting at the time, while local media have published pictures showing bite-marks on her left hand.
"Human bites are more dangerous than dog bites. I now need to take antibiotics," Joner said.
The Cuban embassy in Oslo did not immediately respond to requests for comment. Members of Norway's centre-right opposition have demanded that the diplomat be expelled from the country.
Norwegian Foreign ministry spokesperson Bjoern Jahnsen however said "we have heard nothing about this from the police and we are only familiar with this affair through what has been published in the media".
"If the alleged incident leads to a police report, then the foreign ministry will be drawn into the case," he added.