STOCKHOLM, Sweden — Asos Plc reported its first annual profit decline in three years as the U.K.'s biggest online-only fashion retailer spent more on logistics and technology and after a fire at a warehouse disrupted operations.

Pretax profit fell 14 percent to 46.9 million pounds ($76 million) in the 12 months through August, the London-based company said in a statement today. The average of 19 analyst estimates compiled by Bloomberg was 44.9 million pounds.

"We are in a period of major investment that comes at a short-term cost," Chief Executive Officer Nick Robertson said in the statement. "But the medium-term benefits will be significant."

Asos shares have lost about two-thirds of their value this year as the company struggles to cope with its increasing international scale. The fire at its Barnsley distribution center occurred in June.

Chief Financial Officer Nick Beighton is to become chief operating officer with immediate effect, the company also said. Asos has started a search for a replacement financial director.

By: Katarina Gustafsson; Editors: Celeste Perri, Thomas Mulier and David Risser