A man who wants the pension of his deceased male partner is entitled to the claim, an adviser to the European Union's top court said on Thursday in a case considered a test of gay rights.

The German man, Tadao Maruko, is seeking a widower's allowance of about 6,400 euros ($8,700) a year under an insurance policy after the 2005 death of his registered partner who was insured by the German Theatre Pension Institution.

The institution rejected the claim, saying it only provided pensions for spouses and not for registered partners, leading to a court battle that has ended up in the European Court of Justice (ECJ).

Lawyers for Maruko argued the different treatment was a breach of EU rules against discrimination.

The court adviser said on Thursday that refusal to pay the pension to a registered partner represented "indirect discrimination based on sexual orientation which is prohibited ..." as long as the legal status of married people and registered partners are considered similar by national courts.

The adviser noted the German court that referred the case to the ECJ had expressed its view that those rights were similar.

Opinions from the ECJ's advisers are not binding but are followed in rulings in a majority of cases.