A Dunedin police officer's being treated in hospital after being bottled by an alleged robber.

At around 3.20, officers located and tried to apprehend the alleged offender on Bond Street with pepper spray and a Taser.

One of the officers sustained moderate facial injuries after having a bottle thrown at his head.

"It is extremely disappointing to have an officer injured in this way," Inspector Jason Guthrie said.

"Police regularly display significant courage in situations that challenge their personal safety, and this is a great example of that."

The officer is now in Dunedin Hospital and will likely be released today.

A 20-year-old man's been arrested and will appear in Dunedin District Court tomorrow.