A photo of Kellner pinning the suspect to the ground was trending on social media in Sweden this week.

'My first intervention while wearing a bikini during my 11 years as a police officer,' she wrote on Instagram.

Kellner and three friends were sunbathing on Wednesday in a Stockholm park, a homeless man selling newspapers approached, she told Swedish newspaper Aftonbladet.

After he left, one friend noticed her phone was missing. Kellner and a fellow police officer gave chase.

Kellner said she didn't hesitate to make the arrest while wearing a bikini.

'If I had been naked I would have intervened as well,' she said.

AAP