Amazon announced plans Monday to extend its recently launched payments service for subscriptions at third-party services, stepping up its challenge to eBay's PayPal.

An Amazon spokeswoman said the new feature allows people to use their Amazon accounts for automatic payments of fixed or variable amounts.

"Automatic payments helps businesses that rely upon subscription-based or recurring payments to generate revenue (web and mobile)," the spokeswoman said in an e-mail.

The U.S. online giant said testing in recent months showed "pretty impressive results" and found "customers choosing to use Amazon over other payment methods."

Amazon said the service can be adapted for apps and other services by offering "transparent and low (fee) payment processing."

The move ramps up Amazon's challenge to PayPal, which also seeks to become an online payment option for many types of services.

Amazon launched its payment service last year, allowing people to make one-time payments to third parties. The latest announcement adds recurring payments.