Hollywood action hero Arnold Schwarzenegger was held at Munich airport on Wednesday for failing to declare an expensive watch, a customs spokesman told AFP.

The Austrian-born actor and former governor of California, 76, was detained in the customs area on Wednesday afternoon after arriving from the United States, spokesman Thomas Meister said.

Schwarzenegger was expected to be able to continue his journey later in the day but "the watch will probably have to stay", Meister said.

Criminal proceedings were initiated against the "Terminator" star and former bodybuilding icon for tax evasion, he said.

Tax should have been paid on the watch because Schwarzenegger was intending to sell it in the European Union, according to Meister.

The luxury timepiece was due to be auctioned at a fundraising dinner for Schwarzenegger's climate initiative in Kitzbuehel on Thursday, the Bild daily reported.

Items typically auctioned at such dinners include works of art and signed memorabilia, according to the initiative's website.

The bespoke timepiece was made specially for Schwarzenegger by luxury Swiss watchmaker Audemars Piguet, according to Bild.