The official Twitter photo tool is likely to work in the same way as the existing services by allowing users to upload pictures and share them using shortened URLs.
It would have an advantage over third-party apps because it will be built in, meaning users will not need to navigate away from the site to share their photos.
CEO Dick Costolo is expected to announce the service at the D9 Conference that takes place in the US this week, according to reports.
Twitter was not available for comment in time for publication.
Earlier this year Twitter told developers to stop making their own apps and third-party clients. Following that request Twitter bought UK-based TweetDeck for a reported $40m (£24m).