May 15 (Reuters) - Stockmann Oyj :
* says its group sales amounted to 136.9 million euros in April 2015.
* says sales were down by 23.5 percent on previous year at comparable exchange rates.
* says euro-denominated sales were down by 26.1 percent.
* says decline was due to timing of Crazy Days campaign in Finland; this year the campaign was held in March, instead of April as in previous years. Source text for Eikon: Further company coverage: (Reporting By Helsinki Newsroom)