She was off duty and wearing a bikini, but that did not stop Swedish police officer Mikaela Kellner from catching a suspected thief.

A photo of Ms Kellner pinning the suspect to the ground has been trending on social media in Sweden, and is now proving a hit across the world.

She wrote on Instagram: "My first intervention while wearing a bikini during my 11 years as a police officer."

Ms Kellner and three friends were sunbathing on Wednesday in a Stockholm park when a homeless man selling newspapers approached.

She told Swedish newspaper Aftonbladet that after he left, one friend noticed her phone was missing, so Ms Kellner and a fellow police officer gave chase.

Ms Kellner said she did not hesitate to make the arrest while wearing a bikini, and added: "If I had been naked I would have intervened as well."

AP