Swedish fast-fashion retailer H&M reported weaker-than-expected fourth-quarter sales on Thursday due in part to a late Black Friday, but said sales were up 4 percent in December and January, indicating a better start to the new fiscal year.

H&M's sales in the fourth quarter to Nov. 30 were 62.19 billion Swedish crowns ($5.65 billion), up 3 percent in local currencies, a weaker performance than analysts' mean forecast of 63.48 billion Swedish crowns.

Black Friday landed on Nov. 29 last year, and H&M said more of its sales around that key discounting day were reported as revenues in December, hitting quarterly sales by just under 1 percent.

Operating profit margin for the quarter was 7.4 percent, up from 6.9 percent a year before, as CEO Daniel Erver, who took over a year ago, said investments in marketing were starting to pay off.

"Strong online sales together with improved product presentation and a more inspiring shopping experience, well-received womenswear collections and effective cost control all contributed to a positive development in the quarter," Erver said in a statement.

In a push to make the H&M brand trendier, Erver has hiked marketing spending and hired pop star Charli XCX to model H&M's autumn collection and to perform at free gigs attended by thousands during London Fashion Week and in New York's Times Square.