A Romanian court will on Tuesday resume the trial of six men over the spectacular theft from a Dutch museum of seven masterpieces that are still missing and feared destroyed.

The main suspect, Radu Dogaru, and most of his accomplices have admitted stealing the paintings, which include two Monets, a Gauguin and a Picasso, Maria Vasii, one of the defence lawyers, told AFP.

But one of the six defendants, Adrian Procop, is still on the run and is being tried in his absence.

The judge could choose to adopt a simplified procedure and hand down a verdict rapidly, or he could choose to hear all the evidence and the witnesses, Vasii added.

"But the crime we are talking about shocked the entire world," she said, so the judge would probably take time to hear the facts of the case.

Although the trial opened briefly on August 11, it was adjourned to allow more time for legal issues to be examined.

On that occasion, Dogaru's lawyer said he had offered to return five of the paintings if the trial were moved to the Netherlands, where sentences are lighter.

If convicted in a Romanian court of "theft with exceptionally serious consequences", he faces up to 20 years in prison.

The fate of the paintings however, is still unknown.

Prosecutors fear the masterpieces may be lost forever after Dogaru's mother Olga said she had torched them in a bid to destroy evidence and protect her son.

She later retracted her statement, but experts from Romania's National History Museum said ashes retrieved from her 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, although four of those were oil paintings. A separate investigation to determine exactly what happened to the canvases is under way.

It took less than three minutes for the thieves to take seven works by some of the world's most famous artists from the Kunsthal museum in Rotterdam in the pre-dawn heist last October.

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" in the Netherlands, was 18 million euros ($24 million) according to prosecutors. But at the time of the heist, art experts said the paintings were worth up to 100 million euros.

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

After smuggling the paintings into Romania by road, the group tried to sell them without success. They were caught after a Romanian art expert called in to appraise them for a potential buyer alerted the police.

Dogaru and his alleged accomplices all came from the same region in eastern Romania but lived in The Netherlands.

Dogaru is already known to police, and is under investigation in Romania for murder and human trafficking.