The Love Actually star played the lead role in 2011 film Oka! Amerikee, about a music expert living in the jungles of central Africa, but the shoot was regularly interrupted by rogue army officials.
The film's producer was held for ransom by local warlords, and their attentions turned to Marshall when they realised he was the movie's star.
Marshall tells Radio Times magazine: "I actually got kidnapped while making a film in the Congo jungle, where army warlords are 10-a-penny.
"I mean, I use the word kidnapped very loosely. Basically, the army used to turn up at our unit base and take the producer away whenever they were bored and we would have to pay to get him back.
"And then one day, when they found out I was the main actor on the job, they took me instead.
"So, I say kidnapped, but it involved me being led into the back of a jeep, driven away to some army/police office by drunk guys with machine guns standing around for about three hours, before they bought me back for about $200."