A sneaky swig from a bottle out of a bag at a Dunedin bar led to two arrests and a police officer being assaulted.

Senior Sergeant Anthony Bond, of Dunedin, said a group of people were drinking at a bar in the Octagon, including a woman who was caught taking drinks from a bottle in her bag just after midnight today.

The woman was kicked out of the establishment and she went to confront a group who she believed had dobbed her in.

The group stole her bag and ran off down Princes St, where police located them.

A 32-year-old man advanced on an officer, trying to punch him in the face and grab his groin.

He was arrested for disorderly behaviour likely to cause violence, assault of a police officer, resisting arresting arrest and speaking threateningly.

He would appear in court on July 14.

A 32-year-old female from the group was also arrested because she had a warrant for her arrest.

- Wyatt Ryder, ODT