Google Inc. has agreed to pay at least $19 million in refunds to settle federal allegations that the Internet giant improperly billed parents for unauthorized purchases by their children while using mobile apps.

The company also promised to change its billing practices for so-called in-app purchases “to ensure that it obtains express, informed consent from consumers before charging them for items sold in mobile apps,” the Federal Trade Commission said Thursday.

The unauthorized charges began in 2011 for virtual items purchased on apps sold by Google Play for use on Android mobile devices, the agency said. Some parents complained their children racked up hundreds of dollars in charges that never were authorized.

“As more Americans embrace mobile technology, it’s vital to remind companies that time-tested consumer protections still apply, including that consumers should not be charged for purchases they did not authorize,” said Edith Ramirez, the agency’s chairwoman.

Google agreed to send out a minimum of $19 million in full refunds for the charges.

The company will contact all consumers who made in-app purchases to let them know about the refunds, the agency said.

A Google spokeswoman did not immediately respond to a request for comment.

The agency has been cracking down on unauthorized in-app purchases by children of virtual items for use in games and other apps. The items can cost anywhere from 99 cents to as much as $200.

In January, Apple Inc. agreed to pay at least $32.5 million in refunds to consumers for such purchases.

And in July, the agency filed a complaint against Amazon.com, alleging it unlawfully billed parents millions of dollars for unauthorized purchases through apps on the company’s Kindle Fire and other mobile devices.

Google introduced in-app charges in 2011 and at first billed without any requirement for a password or other authorization, the agency said.