"The already overvalued Swiss franc strengthened further against currencies in all of the Group's important sales regions compared to the first half of the previous year," Swatch said.
Net profit fell to 680 million Swiss francs (559 million euros, USD 757 million).
But sales rose by 8.5 per cent from the equivalent period last year to 4.5 billion Swiss francs at constant exchange rates, Swatch said in a statement.
However, at current exchanges rates, the sales increase was 4.0 per cent, totalling 4.3 billion francs, the group noted.
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Swatch said that it also faced "significant strain" due to a December 29 fire on an electroplating plant -- a key stage in the watchmaking process.
"Although the fire was quickly brought under control, extensive damage and an interruption of business occurred in the electroplating department and the downstream watch movement production," it said.
While the clean-up was completed within weeks of the fire, long delivery schedules for replacement machinery meant that the damaged plant could not be rebuilt as planned in the first half of the year.
Swatch, whose stable of brands includes Flik Flak, Tissot and Longines, said that gross sales in its watches and jewellery division rose by 8.8 per cent at constant exchange rates and 4.3 per cent at current rates compared to the previous year.
"In local currency, all markets except for a small number of European countries remain on a growth course compared to the very high prior-year figures. This is also the case in China," it said.
Marketing investment at the Games had a particular impact on its flagship Omega brand.