ZURICH, Switzerland — Swiss watch exports had their biggest quarterly decline since 2009, as the industry struggles with the strong franc and concern that competition from Apple Inc.'s smartwatch may be denting demand for low-end timepieces.

Shipments declined 7.2 percent in the third quarter, adjusted for working days, the Swiss customs office said Tuesday in a statement. On an unadjusted basis, exports dropped 6.5 percent.

Watch shipments make up about a tenth of Switzerland’s total exports. Swiss watch executives are the most pessimistic in four years as an increasing minority sees a threat from smartwatches, a Deloitte LLP reported showed last month.

LVMH Moet Hennessy Louis Vuitton SE will start selling a TAG Heuer smartwatch next month, while Swatch Group AG unveiled a namesake watch that can make mobile payments in China last week.

By Thomas Mulier; editors: Matthew Boyle, Phil Serafino.