Dunedin - Dunedin police are believed to be investigating an alleged sexual assault in the city involving a Lions Super Rugby player.

According to the Stuff.co.nz website, the alleged incident took place in the hours after the touring Lions team beat the Highlanders 26-22 in their Super Rugby match at Carisbrook on Saturday.

Police are not talking about the allegation, apart from issuing a brief statement saying that there had been an "incident" early on Sunday morning involving an 18-year-old female.

It is understood an 18-year-old University of Otago student has complained that she was sexually assaulted.

Friends of the girl at one of the University's halls of residence say they have been warned not to talk to reporters about the incident.

Otago University communications manager Megan McPherson said the incident was a "police matter".

It is understood police requested video footage from a bar in central Dunedin.

When contacted, Lions coach John Mitchell said he had no information. "This is the first we've heard of it."