The trial of six Romanians accused of being behind one of the most spectacular art thefts ever begins in Bucharest on Tuesday amid fears that masterpieces by Monet, Picasso and Gauguin may have been burned and lost forever.

The mother of the main suspect told police she had destroyed the paintings by torching them in a stove, a statement she later retracted. The fate of the paintings remains unclear.

It took less than three minutes for the thieves to take seven masterpieces by some of the world's most famous artists from the Kunsthal museum in the Dutch port of Rotterdam in the pre-dawn heist on October 16, 2012.

Among the paintings stolen and carried away in burlap sacks were Picasso's "Tete d'Arlequin," Monet's "Waterloo Bridge" and "Femme Devant une Fenetre Ouverte, dite La Fiancee" by Paul Gauguin.

The total value of the haul, dubbed the "theft of the century," was 18 million euros ($24 million) according to prosecutors, while art experts at the time of the heist had claimed the paintings were worth up to 100 million euros.

"The theft was carried out according to a meticulous plan," prosecutors say in the indictment.

Identified by surveillance cameras, "the two responsible for the raid were Radu Dogaru, who was also the leader and the organiser of the criminal gang, and Adrian Procop," the indictment says.

Procop, 21, is on the run and will be tried in absentia.

Dogaru, 29, was arrested in January in Romania along with two accomplices, Eugen Darie and Mihai Alexandru Bitu.

He was already known to police, and is under investigation for murder and human trafficking.

"He confessed and explained everything to investigators," his lawyer Catalin Dancu told AFP, hoping that his client could escape the maximum sentence of 20 years in prison for "theft with exceptionally serious consequences."

Dogaru, Procop and their alleged accomplices Darie and Bitu all came from the same region in eastern Romania but lived in The Netherlands, and were under suspicion for robbery while their girlfriends allegedly were sex workers.

With little knowledge of art but eager to steal valuable old pieces, the group settled on the Kunsthal by chance.

After searching for museums on their GPS, the group initially found themselves at Rotterdam's Natural History Museum, but soon realised its exhibits could not be resold.

They then chanced upon a poster advertising an exhibition of 150 masterpieces from the private Triton Foundation at the Kunsthal.

Despite their value, none of the paintings was equipped with an alarm, Dutch authorities said.

The stolen paintings were transported to Romania by road, then hidden in Dogaru's village, Carcaliu.

The group tried several times to sell the paintings, but without success. A former model, Petre Condrat, accused of being an intermediary, is charged with concealment.

But the art world, the public and investigators will have their eyes trained on Dogaru's mother, Olga, who also stands trial on Tuesday.

After initially claiming that she torched the paintings in a desperate attempt to destroy evidence against her son, she later denied the statement.

"I did not burn the paintings," she said at a preliminary hearing in July.

An analysis by experts from Romania's National History Museum revealed that ashes retrieved from the stove included the remains of three oil paintings and nails from frames used before the end of the 19th century.

The museum could not say whether these were from the paintings stolen in Rotterdam. However, four of the stolen canvases were oil paintings.

Olga Dogaru will also stand trial on Tuesday for aiding and abetting a theft. A separate investigation into the possible destruction of the artworks is pending.

In the quiet village of Carcaliu, there are those who hope the paintings have not been destroyed.

"If they were burned it would be very sad, because they represent the cultural heritage of future generations," said Iacob Iacob, a villager who was home for the holidays from a job in Italy.

The trial's first hearing is set for Tuesday, but no date has yet been set for the next one. Trials in Romania usually last several months.

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