(Adds tweets, data on social media conversations)
Nov 26 (Reuters) - Cyber Monday was on track to bring in a record $7.8 billion in U.S. online sales, but will also test the limits of retailers' e-commerce operations as millions of shoppers scour for steep discounts on everything from Lego sets to big-screen TVs.
Retailers such as Target Corp are offering deliveries with no minimum order limits, pulling out all stops to get customers' attention in a highly competitive market.
U.S. retailers have also bombarded shoppers with thousands of promotional emails, but that drew the ire of several people who complained that they woke up to a deluge of cyber Monday emails compared to years past.
"Yes retailers, I'm aware it's Cyber Monday even without the 150 emails," tweeted Keina (zRealMamaEagle), a user from Delaware.
Retailers have logged $531 million in online sales as of the latest tally and is set to hit $7.8 billion in sales, according to Adobe Analytics, which tracks transactions at most of the top U.S. online retailers.
The numbers, however, pale in comparison with the $30.7 billion sales generated by Chinese e-commerce giant Alibaba Group Holding Ltd on Singles Day earlier this month.
Drawing an estimated 75 million shoppers, the event will severely test retailers' online platforms as well as their delivery operations. If not backed with the right IT infrastructure, the heavy traffic will lead to headaches such as outages and other technical glitches.
As of 10:30 am ET, no big U.S. chain had seen any technical difficulties, according to Website outage tracker DownDetector.com.
On Black Friday, websites of clothing retailers J.Crew, Lululemon Athletica Inc and home improvement chain Lowe's Cos Inc suffered technical issues because of the surge in orders.
Toys are expected to have the biggest discounts on Cyber Monday, Adobe Analytics said, as retailers fill the void left by the bankruptcy of top U.S. toy retailer Toys 'R' Us.
Target was offering 30 percent off on select toys, while Kohl's discounted Lego sets between 30 percent and 40 percent.
Clothing retailers such as Gap and Nordstrom were offering the same discounts as on Black Friday.
Other deals include:
A $198 wool cashmere cardigan being offered at $107 at Ralph Lauren
Sweaters at American Eagle Outfitters being offered at half price
Victoria's Secret selling all bras, excluding PINK, at a 50 percent discount
Shares of Amazon were up as much as 3.2 percent in early trading, while those of Target rose.
Social media conversation tracker Brandwatch said out of 13,000 social media mentions of Cyber Monday (#Cybermonday) the Apple Watch and the Red Dead Redemption 2 video game were two products that stood out.
On Black Friday, online sales jumped more than 23 percent, crossing $6 billion, while online sales surpassed $3.7 billion on Thanksgiving, according to Adobe Analytics.
The National Retail Federation forecast U.S. holiday retail sales, including online, in November and December will increase between 4.3 percent and 4.8 percent over 2017, for a total of $717.45 billion to $720.89 billion. (Additional reporting by Uday Sampath Kumar and Soundarya J in Bengaluru and Melissa Fares in New York; Editing by Bernard Orr and Saumyadeb Chakrabarty)