FRANKFURT—K+S AG, the German fertilizer and salt producer trying to fend off an unsolicited takeover approach, has reported double-digit growth in second-quarter revenue and earnings, helped by better potash prices and the euro's weakness against the dollar.

"The strong performance reinforces our guidance of a significant earnings increase this year," K+S Chief Executive Norbert Steiner said.

K+S, whose board has rejected a near $9 billion approach from Canada's Potash Corp. of Saskatchewan Inc., said on Thursday that after-tax profit rose 46% to €118.7 million ($130.6 million), compared with €81.1 million in the year-ago period. Revenue surged 16% to €914.4 million, while earnings before interests and taxes rose 14% to €179.2 million.

The German group said it benefited from higher prices for deicing salt in North America and the recovery of average prices for its potash and magnesium business unit.

The company spelled out more detailed earnings guidance for the full-year. It now expects operating earnings of €780 million to €860 million, versus €641 million in 2014 and revenue of €4.35 billion to €4.55 billion in 2015, versus €3.82 billion last year.

K+S last week rejected a second takeover approach from Potash Corp. The company said earlier this week that individual shareholders are lining up with the German potash and salt producer's institutional investors to oppose, according to a shareholder survey it conducted.

The takeover fight comes amid weakness in global potash prices particularly since 2013 when Russia's Uralkali pulled out of a sales partnership with Belarus. Regional sales alliances had previously kept potash prices high.

K+S and Potash Corp. both mine potash and a tie-up would create a business that could control as much as 30% of the global market.

Write to Neetha Mahadevan at neetha.mahadevan@wsj.com

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