American Express has launched a ‘Pay By Tweet’ service on Twitter, allowing its cardholders to buy products by sending a message on the social network.

“We’re turning a tweet into an actual transaction,” head of digital partnerships and development at American Express Leslie Berland told The Financial Times.

Using the mechanism, users who have linked their Twitter and Amex accounts will be able to take up offers from merchants on the network by using a hashtag included in the ...