BENTONVILLE, Ark. -- Wal-Mart Stores Inc. is testing drones that it says will help it manage its warehouse inventory more efficiently, and which it said Thursday could be rolled out in the next six to nine months across its distribution centres.

The move is another sign of how the nation's largest retailer is seeking to compete against online leader Amazon.com, which is testing drones to deliver packages.

During a media tour Thursday at a distribution centre, Wal-Mart offered a peek at a drone that flies around the massive centre, captures images in real time and flags the misplaced items. The drone takes 30 pictures per second.

Wal-Mart says using the drones enables it to check inventory in about a day or less, instead of a month that it takes manually.

Right now, employees stand on lifts that go up and down the stacks, and scan items to make sure that boxes are in the right place.

Shekar Natarajan, Wal-Mart's vice-president of logistics strategy, told reporters the technology is custom-built on top of the drone and is proprietary for Wal-Mart. A control tower will oversee the images on a screen and will send alerts when items are flagged so that workers can go back to the stacks to fix the issue.

Amazon, meanwhile, had said in December that its drone program, Prime Air, will one day deliver packages up to 5 pounds in 30 minutes or less. The Federal Aviation Administration currently bans commercial drone flights but has granted several thousand waivers. It has granted Amazon approval to fly drones for research.

The drones will fly under 400 feet and weigh less than 55 pounds, according to details posted on Amazon's website. Amazon says Prime Air will start once government regulations are in place to support it. It has development centres in the U.S., the U.K. and Israel.

Last year, Wal-Mart asked the FAA for permission to test drones. Wal-Mart also said it is testing artificial intelligence and virtual reality technology in the warehouses, but declined to elaborate.