Promoted tweets were introduced to the desktop version of Twitter almost two years ago, allowing companies to issue promotional messages in users' timelines.
However, more than half the microblogging site's 100 million active users now regularly access the service on a mobile device, and so Twitter has moved to reach this new audience with advertising.
Users of Twitter apps on iPhone and Android will in the coming weeks start seeing promoted tweets in their timeline. This will start with a "small number" of promoted tweets from brands and companies that users already follow.
The tweets will only appear where they are "relevant", and be clearly designated as "promoted".
Twitter said that the move is aimed at ensuring "people see important tweets from the brands they care about". It added that any messages not relevant to users can be dismissed from their timelines "with a single swipe".
Promoted accounts may also appear in the 'Who to Follow' recommendations on people's timelines, said the firm.
"We've had a simple philosophy since we first launched ads on Twitter, and it's this - we strive to create products that put users first, and continue to enrich your Twitter experience," said Twitter in a blog post.
"Today's news represents another important step in our advertising efforts, and we hope you like it."
Yesterday, Twitter announced a partnership with UK firm Datashift to enable businesses to access every single tweet posted about them by a user dating back two years.
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