NEW YORK, United States — Walmart on Thursday posted a 40 percent rise in US e-commerce sales, higher than the 33 percent growth witnessed in the previous quarter, and its comparable sales grew the most in a decade, sending its shares up 9 percent in premarket trade.

Walmart also raised its annual earnings outlook and said it is on track to increase US e-commerce sales by 40 percent for the full year.

Excluding special items, like a charge related to the sale of a majority stake in Walmart Brazil, adjusted earnings came to $1.29 per share in the second quarter ended July 31. The average analyst estimate was $1.22 per share, according to Thomson Reuters I/B/E/S.

Sales at US stores open at least a year rose 4.5 percent, excluding fuel price fluctuations, higher than analyst forecasts of 2.38 percent, according to Thomson Reuters I/B/E/S.

The growth was led by strong performance in grocery, apparel and seasonal merchandise, which rebounded in the second quarter after a slow start in April. Walmart has recorded nearly four straight years of US growth, unmatched by any other retailer.

Total revenue increased 3.8 percent to $128 billion, beating analysts' estimates of $125.97 billion.

The company's gross margins continued to remain under pressure from price-cutting, freight costs and investments in e-commerce. Gross margins were down 17 basis points during the second quarter, the company said.

Walmart's shares were up 9.88 percent at $99.14 in premarket trade. The company's stock has fallen around 9 percent since the start of the year.

By Nandita Bose; editor: Frances Kerry