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.
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"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.