The Neiman Marcus homepage has been mostly unavailable since 8 am ET on Friday, CNBC reported, citing data from website performance monitor Catchpoint Systems. (http://bit.ly/1kY3gLk)

The site has been slow to load and erratic since then.

Neiman Marcus spokeswoman Ginger Reeder said she could not confirm the time of the outage, but said the company was working to restore the website.

"We are working fervently to get the site back up. I don't have any further updates at this time," Reeder said.

The outage could hurt upscale retailer Neiman Marcus during one of the most important days for holiday shopping, at a time when more shoppers are shopping online.

According to software firm Adobe Systems Inc's Digital Index, shoppers in the United States spent $822 million online between midnight and 11 am ET, a 15-percent increase from 2014.

(Reporting by Anya George Tharakan in Bengaluru; Editing by Anil D'Silva)