Internet sales jumped more than 30 percent on Cyber Monday, making it the biggest online shopping day ever, according to data released on Tuesday.

Walmart.com, the online division of Walmart U.S., had its best sales day in history, a spokeswoman said.

Cyber Monday also was a record day for sales of Amazon.com Inc’s Kindle devices, the online retailer said, without specifying the number sold.

Still, eBay Inc, operator of one of the largest online marketplaces, outperformed its arch rival Amazon.com over the crucial first five days of the holiday shopping season, according to one closely watched measure.

Cyber Monday has been the biggest online shopping day in recent years, as workers return to offices and make holiday purchases on their computers. This year, the boom in smart phone and tablet adoption has added extra fuel to online shopping.

Cyber Monday sales online jumped 30.3 percent from the same day last year, according to International Business Machines Corp, which analyzes transactions from 500 U.S. retailers.

Mobile devices accounted for 18 percent of visits to retailer websites and 13 percent of sales on Cyber Monday. That was up 70 percent and 96 percent, respectively, compared with the same day last year, IBM reported.

To that end, Walmart.com said Cyber Monday online traffic from Walmart’s mobile apps jumped 280 percent versus a year ago.

On Monday, when retailers offered big Cyber Monday online deals, web shopping peaked at 11:25 a.m. EST (1625 GMT), IBM said. That timing suggests shoppers continue to check out online offers while still at work, even though more people have high-speed Internet access at home than in previous years.