Arnold Schwarzenegger was detained at an airport in Germany after failing to declare a luxury watch.

The Terminator actor, 76, was held by customs officers in Munich on Wednesday (Jan 17) "under tax laws" for several hours after flying in from Los Angeles after he was taken pulled aside to have his luggage inspected and officials found a custom-made watch from Swiss brand Audemars Piguet in his bag worth more than US$21,000 (S$28,000).

Munich's customs spokesman Thomas Meister told German newspaper Bild the timepiece should have been registered because it is an import and they have now "initiated criminal tax proceedings" over the incident.

According to Bild, Arnold called in his lawyers after being questioned for nearly four hours and was allegedly slapped with a €35,000 (S$51,000) fine for failing to declare the watch.

He was reportedly flying with his physiotherapist partner Heather Milligan, 49, was released and allowed to continue on his journey to Austria shortly before 5pm local time.

In a photo obtained by Bild, the actor did not appear fussed by the situation as he was seen smiling to the camera as he held up a box with the watch presumably inside.

A source told Page Six the actor was "never asked to fill out a declaration form and he answered every question from customs officers honestly".

They added: "He co-operated at every step even though it was an incompetent shakedown, a total comedy of errors that would make a very funny cop movie."

Page Six said a source told them Arnold agreed to pre-pay potential taxes on the watch but officers allegedly had issues using a credit card machine for up to an hour.

The insider added Arnold was then brought to a bank to withdraw from a cash machine, but the amount needed exceeded the funds and the bank was already closed.

They said: "When he returned, a new officer brought a new credit card machine that worked."

Bild said Arnold "initially took the interrogation fairly calmly, but then the time and the procedure got on his nerves".

Arnold, who has dual Austrian and US citizenship, was on his way to attend a charity auction being held on Thursday in Kitzbuhel, Austria, and he is thought to be going to auction his watch at the event.

An insider told Page Six: "The Schwarzenegger Climate Initiative will properly report it, as all of Arnold's non-profits do," an insider says.

"His charity auctions raise millions of dollars every year for after-school programs for kids all over the US and environmental work around the world.

"We hope Germany spends as much energy turning around their economy as they do asking for tax payments for people's property they bring into the country, and we hope next time they don't make him pay taxes on his suits."

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Source: Bang