* Q1 net profit 455 mln euros vs consensus for 421 mln euros
* Q1 sales 5.7 bln euros vs consensus for 5.4 bln
* Sales up 31 pct in North America, up 30 pct in China
* Reebok sales rebound
* Shares indicated up 0.6 pct, among top Dax gainers (Adds details, background)
BERLIN, May 4 (Reuters) - German sportswear firm Adidas reported a bigger-than-expected increase in first-quarter sales and profits on Thursday, as it outpaced arch-rival Nike in North America and China and grew fast online.
Adidas also reported a rebound in sales for its struggling Reebok brand, with quarterly growth up 13 percent, compared to just 6 percent in 2016, which Adidas said was driven by the training category and retro styles.
Adidas said net profit rose 30 percent to 455 million euros ($495.7 million) on sales up 19 percent to 5.67 billion euros, ahead of average analyst forecasts for 421 million and 5.4 billion respectively, according to a Reuters poll.
Adidas said growth was particularly strong in ecommerce, with revenues up 53 percent, and in North America and China, where sales grew 31 percent and 30 percent respectively.
Nike reported sales rose just 3 percent in North America in the quarter ended Feb. 28, while they were up 9 percent in Greater China, falling short of double-digit growth for the first time in at least nine quarters.
After losing ground to its U.S. rival for years, Adidas launched a big marketing drive in the United States to challenge Nike on its home turf, prompting consumers to snap up its Boost running shoes and retro styles like Superstars.
Shares in Adidas have risen 21 percent so far this year.
German rival Puma has also reported strong demand in the first quarter, prompting it to lift its profit and sales guidance for 2017.
New Adidas Chief Executive Kaspar Rorsted has also announced a big push online, in March doubling the ecommerce sales target for 2020 to 4 billion euros out of an expected 25 to 27 billion euro total, and from 1 billion achieved in 2016.
$1 = 0.9179 euros Reporting by Emma Thomasson; Editing by Victoria Bryan