One of Gustav Klimt's most famous paintings will not be returned to the heirs of its Jewish former owner, in a case that has tested Austria's laws on restitution of looted art.

The law, which is often applied in cases linked to the country's Nazi past, was updated in 2009 to include works which were sold rather than stolen, but whose owners had been put under pressure to part with their property.

The 34-meter-long "Beethoven Frieze," completed in 1902 as an homage to the German composer's Ninth Symphony, used to belong to members of the Lederer family but was seized when they fled to Switzerland after Nazi Germany annexed Austria in 1938.

Erich Lederer got the masterpiece back after World War II, but he was not allowed to export his many other artworks unless he sold the painting to Austrian government at a discount, the family's lawyers say.

He eventually sold it for $750,000 in the 1970s, and it now hangs on public display in Vienna's Secession Building.

Austria, which returned several works by Klimt's near contemporary Egon Schiele to Lederer's heirs in 1999, said it would follow an expert panel's decision on Friday that the painting was lawfully sold to the state.

One of the lawyers representing some of Lederer's heirs said he rejected the decision and planned to take the case to the European Court for Human Rights in Strasbourg or a court in the United States.

Swiss-based lawyer Marc Weber said the decision-making process regarding Austria's restitution law was not transparent for the heirs of former owners.

Alfred Noll, another lawyer representing a group of Lederer's heirs, echoed Weber's criticism but said he would not take further action, according to the APA news agency.

Culture Minister Josef Ostermayer said he was glad the frieze would remain on show for people in Austria to visit.

Reuters