Twitter said Wednesday that it is adding a photo-sharing option for its users, a move that could deal a blow to existing services such as Twitpic and yfrog. Twitter chief executive Dick Costolo also announced at the All Things Digital technology conference here that the San Francisco-based service was upgrading its search function. Twitter will begin allowing users to upload pictures and attach them to \"tweets\" directly from Twitter.com, Costolo said. \"It\'s part of the native data of the tweet,\" he said, adding that the decision to launch a photo-sharing service stemmed from a \"need to remove the friction of adding photos to Twitter.\" Twitter said that its official mobile applications will also provide a photo-sharing feature and the service will be available in the next several weeks. As for search, Twitter said it will begin showing related photos and videos in search results. Twitter\'s launch of a photo-sharing option poses a potentially serious threat to various third-party services people currently use to post pictures on Twitter. It is the latest move by the company to provide in-house services and features for using Twitter. Last week, Twitter announced it had bought TweetDeck, a popular application for using the service. TweetDeck, which was founded in 2008, is a favorite of heavy users of Twitter, allowing them to view tweets in various different ways and to organize their messages into columns - features not offered on Twitter\'s own website.