Hamas on Monday said "one of its senior leaders" and his son have been in Saudi custody since April of this year, reports Anadolu Agency.
In a statement, the group said the Saudi security services arrested Mohammad Al-Khodari, who has been living in Saudi Arabia for three decades and described the arrest as a "reprehensible action".
The statement mentioned that Al-Khodari was responsible for administering the relations with Saudi Arabia for over the past two decades and he got several leading positions in the movement.
"Hamas kept silent over the past five months of his arrest to allow for mediations efforts but these efforts have yet to bear fruit", it said.
Euro-Mediterranean Monitor for Human Rights, a Geneva-based group, also said that the Saudi authorities detain around 60 Palestinians in its jails.
In a statement, the rights group called on Saudi King Salman bin Abdul Aziz to order the immediate release of the detainees, especially those who are detained without specific indictments.