Amazon.com Inc is limiting sales of its own at-home COVID-19 test kits to ten units per customer following actions taken by retailers including Walmart Inc and CVS Health Corp, as more people test for the Omicron variant of the coronavirus.

The fast-spreading variant has become dominant in the United States and testing has rapidly risen as many consumers make plans for holiday travel and shopping.

Amazon's own COVID-19 Test Collection Kit and iHealth's COVID-19 Antigen Rapid Test were unavailable on the e-commerce site.

An Amazon spokesperson said the company is facing inventory shortages on some COVID-19 tests due to increased demand.

The company on its website asked customers to not collect or mail samples starting Wednesday to Sunday as they will not be shipped to laboratories and due to holiday schedules at package delivery company United Parcel Service.

The Amazon spokesperson said the company has also allowed third-party sellers to set their own limits on how many test kits can be sold on its website.

Walmart set a limit of eight tests for each online order, while CVS capped sales of test kits to six per person. Walgreens Boots Alliance Inc said it would limit both online and in-store purchases of test kits to four per customer.