The painting depicts a girl shooting flowers with a hose bell, and is found on a building in the English city of Bristol. On Saturday, the work had been overpainted with pink graffiti.
Banksy had not signed the work in the usual order, but on Valentine's Day, the artist confirmed via Instagram that he was behind the painting that has now been vandalized.
Banksy began his career with "ordinary" graffiti in the early 1990s and has since become a world name for his satirical works with an emphasis on politics, ethics and culture. Banksy's identity has never been revealed.