Apple announced further details about its Watch, including how the NFC-based device can be used for mobile payments.

Users can tap-and-pay in shops and restaurants with the Apple Watch but they do need to already own an iPhone 6, 6 Plus, 5, 5c or 5s.

As Recode explained, users will need to open the Apple Watch app on their iPhone, then tap the Passbook and Apple Pay options in the app to add a credit or debit card which will be used for in-store payments.

The Apple Watch app is being installed on iPhones as part of an iOS update.

No actual card or account information is stored on the watch. Instead the device holds what is described as a unique placeholder code, which is only matched with a credit card account after the watch has been used to make a payment.  A shop or restaurant sends the placeholder code to a bank or credit card when a user makes a payment. The bank or credit card recognises the code and authorises the payment.

So while the user needs an iPhone initially to set up the watch for Apple Pay, they can afterwards make in-store payments with just the watch.

Citi and Mint are among the first financial services firms with apps for Apple’s watch.

In his presentation about the new device, Apple CEO Tim Cook touched on the growth of the Apple Pay service, although there was no indication about if or when it intends extending it beyond the US market.

Stating that the service has “forever changed the way we pay for things”, he said that the number of locations it can be used at has tripled in three months to almost 700,000, with The Coca-Cola Company planning to support it in 100,000 vending machines by the end of this year (up from 40,000 today).