BELGRADE, Serbia -- The grandfather of Jelena Djokovic, the wife of Novak Djokovic, has been found tied up in a field after unknown assailants broke into his house in central Serbia.

Djokovic's press team said in a statement Thursday that the family is in "complete shock over what happened" to 85-year-old Miloslav Radisavljevic.

They say attackers broke into Radisavljevic's house, kidnapped him and took him to a field several miles away.

Police said, without identifying Radisavljevic, that they found a man early Thursday tied to a power pole close to his house in Ljig, some 50 kilometers (about 30 miles) south of Belgrade.

The man told the police he was robbed by two masked assailants of about 220 euros ($260) and a cellphone. Police said the man had no visible injuries.