BERLIN (Reuters) - German e-commerce investor Rocket Internet <RKET.DE> reported a first-half consolidated loss of 617 million euros ($691 million)mainly due to impairments at Global Fashion Group.

Worries over the value of the company's investments have knocked shares in Rocket, down 33 percent this year, after it wrote down the valuation of GFG, which includes online fashion businesses Zalora in Southeast Asia, Dafiti in Latin America and Lamoda in Russia.

Rocket Internet said late Thursday its first-half results took a 383 million euro hit from the GFG unit, in which Swedish group Kinnevik <KINVb.ST> is a co-investor. The German company values holdings on a fundraising basis and GFG's last funding round closed in July.

Rocket Internet said it took other impairments and fair value adjustments, but did not provide details.

Chief Executive Oliver Samwer said the group remained committed to its goals.

"We still expect at least three of our selected portfolio companies to turn profitable by the end of 2017, and that the aggregate EBITDA losses of the selected portfolio companies will have peaked in 2015," he said in a statement.

Rocket Internet is due to report full first-half results on Sept. 22.

($1 = 0.8933 euro)

(Reporting by Victoria Bryan; Editing by Leslie Adler)