A woman arrested in Osaka on Wednesday on suspicion of defacing traffic signs with artsy, humorous stickers has admitted to vandalism, police said.

"I did it as a form of artistic expression but now I deeply regret it," police quoted 43-year-old Mami Urakawa as saying.

Urakawa's apparent accomplice, French national Clet Abraham, who describes himself as a street artist, was not detained. Within hours of Urakawa's arrest, her photo appeared on Abraham's social media accounts.