BERLIN -- A cousin of the late German collector Cornelius Gurlitt is laying claim to his priceless art trove, raising the possibility of a legal battle as a Swiss museum that Gurlitt named as his heir prepares to announce whether it will accept the collection.

Gurlitt's cousin, Uta Werner, applied Friday for a certificate of inheritance to the Munich court that is handling Gurlitt's estate, according to a statement released by her spokesman Thomas Pfaff. She is supported by her children and other relatives, he added.

German authorities in 2012 seized 1,280 pieces from Gurlitt's apartment while investigating a tax case, including works by Pablo Picasso and Marc Chagall. Gurlitt died in May.

He designated Switzerland's Kunstmuseum Bern as sole heir to his long-hidden collection with a six-month deadline for the museum to decide whether to accept the bequest. The museum will announce its decision Monday. On Friday, it denied reports that it already decided in favour.

Shortly before he died, Gurlitt reached a deal with the German government to check whether hundreds of the works were looted from Jewish owners by the Nazis. Authorities say that deal is binding on any heirs.

Gurlitt's relatives originally had planned only to prepare themselves for the possibility of the museum rejecting the collection, Friday's statement said. However, they changed their minds because a report by a psychiatrist has now raised serious doubts over Gurlitt's competence to make a will, the statement added.

The Munich court, whose press office did not immediately return calls for comment, now must review the will's validity to see if there are any "reasonable doubts," the statement said.

The family stressed its commitment to restituting any looted art and a transparent effort to clarify the art works' origins. The statement said they support handing back works already identified as looted art right now.