Shares in Europe's biggest online fashion retailer Zalando rose as much as 12 percent in their Frankfurt debut, valuing the company at about 6 billion euros ($7.6 billion).

Shares in the Berlin-based company, which had been priced at 21.50 euros, started trading at 24.10 euros each but by early morning had pared gains to trade at 22.35 euros in one of Germany's biggest technology flotations in years.