LONDON, United Kingdom — Asos Plc, the U.K.'s largest online- only fashion retailer, reported lower first-quarter sales growth than analysts anticipated as trading conditions abroad "remained challenging."

Retail sales advanced 8 percent in the three months through November, the London-based company, which sells Vivienne Westwood clothing and Vans shoes to twenty-somethings, said in a statement today. The median of 14 analyst estimates compiled by Bloomberg was for 9 percent growth. U.K. retail sales grew by 24 percent while international sales declined by 2 percent.

Asos shares have lost 61 percent in 2014 after more than doubling in both of the previous years. Sales growth has slowed, particularly outside the U.K., where currency movements have made its clothes relatively more expensive. A fire at a distribution center disrupted business in June.

"September and October were challenging," Chief Executive Officer Nick Robertson said in the statement. "Our sales have since gathered momentum and we had our biggest ever trading week over cyber weekend in November."

Asos said it has now introduced zonal pricing in the U.K., Australia and France to improve performance.

By Katarina Gustafsson; editors: Celeste Perri, Kim McLaughlin, Robert Valpuesta.