Nokia warned operating profit margins at its key phone unit would slip in coming quarters after reporting better than expected January - March earnings.
January-March underlying earnings per share fell to €0.13 from €0.14 euro a year earlier, but beat analysts' average forecast for €0.10 euro.
Nokia's market share fell to 29 per cent from 33 per cent a year earlier as nimbler Asian rivals ate into its dominant position in cheaper phones and it continued to lose out in more expensive smartphones to Apple and others.
To turn around its smartphone fortunes, Nokia's new chief executive Stephen Elop in February unveiled a deal to start using Microsoft software instead of its own Symbian platform.
Nokia said the two firms had signed a definite deal.