FRANKFURT, Germany — German e-commerce investor Rocket Internet's investors need to buy into its five to 10 year plans rather than focus on short term market fluctuations, its founder Oliver Samwer told a German newspaper.

Europe's top Internet group has faced increasing concerns from investors about the scale of losses at its start-ups ranging from online fashion to food delivery, as well as delays to planned listings due to volatile markets.

The stock has tumbled in recent weeks following a cut in the valuation of its fashion e-commerce sites to €1 billion ($1.1 billion) in late April, a third of the figure put on the business when it last raised funds in August.

Rocket shares were trading at €20.06 at 08.49 GMT on Monday, down from a year high of €46.65 on May 4 last year.

Asked why Rocket had to raise capital so quickly for Global Fashion Group (GFG), which groups sites in six emerging markets, Oliver Samwer told Sueddeutsche Zeitung in an interview published on Monday that business was tough in some countries, like India, and liquidity needs possibly evaluated wrongly.

By: Alexander Huebner and Tina Bellon; Editor: Alexander Smith.