An old map believed to mark the spot where German soldiers hid treasure worth millions of euros during World War Two sparked the imagination of amateur treasure hunters in the Netherlands this week.

Armed with metal detectors and shovels, groups wandered through the fields surrounding rural Ommeren in the east of the country after the map was made public by the Dutch National Archive on Tuesday.

The archive said the map was believed to indicate where Nazi soldiers had hidden four large boxes filled with diamonds, rubies, gold, silver and all sorts of jewelry which they had looted after an explosion at a bank in August 1944.

The map was obtained from a German soldier shortly after the war by the Dutch institute that was tasked with tracing German capital in the Netherlands after the country was freed from Nazi occupation in 1945.

The research file which held the map was released this week as the maximum period of 75 years during which it could be held confidential had lapsed.

Although the existence of the treasure could never fully be confirmed, the institute undertook various failed attempts to find it in 1947, National Archive spokeswoman Anne-Marieke Samson told Reuters.

"We don't know for sure if the treasure existed. But the institute did a lot of checks and found the story reliable," Samson said.

"But they never found it and if it existed, the treasure might very well have been dug up already."

But the small chance of finding any valuables did not deter the amateur gold-diggers.

"I see groups of people with metal detectors everywhere," 57-year old Jan Henzen told Reuters as he took a break from his own search.

"Like a lot of people, the news about the treasure made me go look for myself. The chance of the treasure still being here after 70 years is very small I think, but I want to give it a try."

Former Ommeren mayor Klaas Tammes, who now runs the foundation that owns the lands that might hide the treasure, said he had seen people from all over the country.

"A map with a row of three trees and a red cross marking a spot where a treasure should be hidden sparks the imagination," he said.

"Anyone who finds anything will have to report it to us, so we'll see. But I wouldn't expect it to be easy."