"Copenhagen police arrested four men on the evening of Thursday, September 16, after they were caught redhanded as they were showing the (Rembrandt) painting to a potential buyer in a Copenhagen hotel," a police statement said on Friday.
Copenhagen police spokesman Flemming Steen Munch said that four men, two Iraqis, a Swede and a Gambian national, had been arrested after being caught trying to sell the Rembrandt.
"They are suspected of dealing in stolen goods," he said, adding that police were not aware of the whereabouts of the missing Renoir.
A Danish court on Friday was expected to remand the four men in custody pending trial.
"We had been keeping them under surveillance for some time because we had the feeling they were going to try to unload a painting in Copenhagen," criminal police inspector Per Larsen told news agency Ritzau.
Nine men have already been handed heavy prison sentences in Sweden for their involvement in the spectacular heist, with a 47-year-old Swede currently serving an eight-year sentence for masterminding the robbery.
Nine men are in jail for
involvement in the heist
Steen Munch refused to comment on whether the four men arrested in Copenhagen were suspected of being linked to the Stockholm robbery.
"We are overjoyed," National Museum spokeswoman Lena Munther said after receiving word from Danish police that the Rembrandt had been recovered.
The timing was especially good, she said, since "this portrait plays a central role in a new exhibit opening next week, entitled The Dutch Golden Age: Rembrandt, Frans Hals and their contemporaries".
"We hope we get it back in time for the opening ... on September 22 ... but we don't know yet," Munther added.
The work, a self-portrait of the artist that has been valued at some $37 million, was stolen along with two paintings by French impressionist Pierre-Auguste Renoir during an armed heist at Sweden's National Museum on 22 December 2000.
It was just five minutes before closing when three masked and heavily armed men walked into the museum, located in the centre of the Swedish capital, and snatched the precious works of art from the walls as numerous witnesses looked on.
The three robbers threw spikes onto the road to slow the police chase and set several parked cars on fire before jumping into a speedboat waiting for them at the waterfront museum and fleeing away into the darkness.
"We had been keeping them under surveillance for some time because we had the feeling they were going to try to unload a painting in Copenhagen"
Criminal Police Inspector,
Investigators recovered the boat, a five-metre fibreglass vessel with a single outboard motor, about two hours after robbery on the banks of the Maelar lake in southern Stockholm, but the three men and the paintings had vanished.
The three paintings were at the time valued at $30 million.
One of the Renoirs, Conversation, was found in central Stockholm on 5 April 2001 by police investigating a drugs case, but the French painter's Young Parisian remains missing.