Spain's Prado Museum on Thursday announced a list of 62 artworks seized during the 1936-39 civil war and under Francisco Franco's dictatorship, and announced a research project that could lead to the works being returned to their legitimate owners.

Among the works are paintings by 17th century Flemish artist Jan Brueghel the Younger and Spanish impressionist Joaquin Sorolla, according to the list.

The two centuries-old museum said in a statement it had set up a research team to study the 25 oeuvres and determine if there are other works that were also confiscated.

"The project aims to clarify any doubts that may exist regarding the works' history and context prior to their cession to the Prado's collections, which, in fulfilment of all legal requirements, may result in works being returned to their legitimate owners," it said.

The findings of the research, to be led by senior professor and expert on cultural heritage and the Civil War Arturo Colorado, are expected by early 2023.

More than half a million people died during the Spanish Civil War and an estimated 150,000 were killed later in repression by Franco's 1939-75 dictatorship, historians estimate.

None of the works on the list are on display at the museum that is part of Madrid's "Golden Triangle of art" along with the Reina Sofia and Thyssen galleries. One of the capital's most famous landmarks, the Prado contains over 7,000 of the world's finest paintings and other works of art.