Twitter last month announced it would begin testing Promoted Tweets and Promoted Accounts in the timelines, searches and suggested follows on its mobile apps. Now the company says it will expand that effort by allowing advertisers to target campaigns specifically to iOS and Android users, as well as those on other mobile devices, PCs or laptops.

Twitter will also begin to allow brands to target Promoted Tweets in the timelines of mobile users that share similar interests with their existing followers.

“Mobile device targeting is great for brands that want to increase the prominence and reach of their message to a particular type of mobile user. For example, mobile game and app sellers can now pinpoint the users who are likely to purchase their products,” noted the company in a blog post today.

Twitter cited American Express, Samsung and Verizon as marketers that are using Promoted Tweets to reach consumers on mobile devices.

Reactions to the new mobile ad options introduced three weeks ago had been positive, the company noted -- paving the way for the latest upgrades. Originally, Promoted Trends and Tweets only appeared in search and Promoted Tweets only in the timeline on Twitter mobile (m.twitter.com).