Madonna has stepped up security on her world tour after receiving death threats in Serbia, according to a new report.

The Material Girl arrived in Belgrade, Serbia in disguise to perform her Sticky & Sweet concert in front of 30,000 fans on Monday.

The controversial star took extra precautions after receiving threatening messages from Balkan fanatics, hiring a posse of bodyguards to protect her as she took the stage in the Serbian capital for the first time, reports British tabloid The Daily Star.

The worried singer will also be accompanied by the minders in neighboring Romania, where she is set to play a gig on Wednesday.

Source, Bauer-Griffin