Jack Dorsey is CEO of both Twitter and Square

Square is allowing some people to test a feature on its money transfer app Cash that enables them to buy and sell bitcoin.

A number of Cash users noticed the new feature, and took to Twitter to voice their surprise.

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Users were able to swipe right from their Cash Card page to buy bitcoin.

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The feature also shows the current price of bitcoin against the U.S. dollar.

Jack Dorsey, the CEO of Square and Twitter, has said that bitcoin is more of an investment vehicle than a means of payment. Dorsey said he has himself invested in the cryptocurrency.

A Square spokesperson confirmed that the firm was piloting the feature with a small number of Cash users.

The spokesperson said: "We've found that (our customers) are interested in using the Cash app to buy bitcoin. We're exploring how Square can make this experience faster and easier, and have rolled out this feature to a small number of Cash app customers.

"We believe cryptocurrency can greatly impact the ability of individuals to participate in the global financial system and we're excited to learn more here."