BERLIN -- A massive gold coin issued by the Royal Canadian Mint has been stolen from a museum in Germany.

Police in Berlin say thieves broke into the German capital's Bode Museum before dawn Monday and made off with the 100-kilogram gold coin worth millions of dollars.

The "Big Maple Leaf" coin, which is three centimetres thick with a diameter of 53 centimetres, has a portrait of the Queen on one side and maple leaves on the other.

The museum, which has one of the largest coin collections in the world, said on its website that coin has been on loan in its numismatic collection since 2010.

It was issued by the Royal Canadian Mint in 2007 and it is in the Guinness Book of Records for its purity of 999.99/1000 gold.

Royal Canadian Mint spokesman Alex Reeves says the coin does not belong to the mint and the owner is unknown.

He said it has a face value of $1 million, but by weight alone it would be worth almost US$4.5 million at market prices.

The mint is still in possession of the original "Big Maple Leaf" coin, which Reeve said was made 10 years ago when the mint launched its one-ounce gold bullion coins.

Reeves said once the original "Big Maple Leaf" coin was unveiled, several people came forward asking to buy one.

"So then it became a product that was made on demand and customers who made a non-refundable deposit on the coin had one manufactured for them," Reeves said.

A total of five coins were produced and sold that way, he said. The one stolen in Germany is one of those five.

Museum spokesman Stefen Petersen said Monday the thieves apparently entered through a window at about 3:30 a.m., broke into a cabinet where the coin was kept, and escaped with it before police arrived.

He added that a ladder was found by nearby railway tracks.

--With files from The Associated Press