Singer Madonna performs at the Valle Hovin Stadium in Oslo July 28, 2009. REUTERS/Scanpix/Kyrre Lien

Several polish nationalists have accused Madonna of being a crypto-Satanist for planning her first Polish concert on a Christian holy day.

Madonna has upset many believers in devoutly Roman Catholic Poland by selecting August 15 to perform her debut concert in Poland, which also happens to be the day when Christians mark the Virgin Mary's ascension to heaven.

Some locals had threatened to boycott the gig but called the protests off over fears it could inspire riots.

However, Marian Baranski, deputy head of the Faith and National Tradition Defence Committee 'Pro Polonia,' said they are very upset about Madonna's gig, according to Reuters.

Madonna specialises in offending religious feelings...It is possible to suspect her of being a crypto-Satanist, he said.

This is not the first time that Madonna - whose very name signifies the Virgin Mary - has upset conservative Christians. She previously kissed an actor who was playing Jesus in her Like a Prayer music video and staged a crucifixion scene in her last world tour.

Madonna sneers at Jesus Christ, the symbol of the cross and all Christians, said Zygmunt Wrzodak, a former member of the Polish parliament.

Madonna has not yet released any change of date for this controversial concert.

She is currently on her Sticky & Sweet tour is scheduled to conclude in Israel on September 2.