Salman al Awdah, a prominent Muslim preacher and member of the IUMS's board of trustees, along with over 20 others including Awad al Qarni and Ali al Omary were detained over the weekend.
Saudi Arabia is yet to issue any official statement regarding the reported arrests.
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In its statement on Monday, the IUMS said the scholars "should not be used as pawns in political disputes", referring to the crisis between Qatar and four other Arab states - Saudi Arabia, the United Arab Emirates (UAE), Bahrain and Egypt.
"In regards to the crisis [with] the Gulf Cooperation Council (GCC) member states, Awdah has done nothing but call for unity between these brotherly countries," the statement added.
Saudi Arabia, the UAE, Bahrain and Egypt cut diplomatic and transport links with Qatar in June over its alleged support for militants, a charge Doha denies.
The IUMS is an organisation of Islamic theologians headed by Chairman Yusuf al Qaradawi and headquartered in Qatar. Some 90,000 Muslim scholars are connected through the union, which claims to bring together Sunni and Shia Muslims.
All the arrested scholars are outside the state-backed clerical establishment but have large online followings. They have previously criticised the government but more recently kept silent or failed to publicly back Saudi policies, including the rift with Qatar over supporting the Muslim Brotherhood.
Awdah was imprisoned from 1994-99 for agitating a political change and leadership of the Brotherhood-inspired Sahwa (Awakening) movement. He later called for democracy and tolerance during the ‘Arab Spring’ uprisings of 2011.
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Saudi officials have dismissed reports that the king may soon pass the throne to Crown Prince Mohammed bin Salman, who already dominates economic, diplomatic and domestic policy.
However, the al Saud family has always regarded militants groups as the biggest internal threat to its rule over a country in which appeals to religious sentiment cannot be lightly dismissed and an al Qaeda campaign a decade ago killed hundreds. In the 1990s, the Sahwa demanded political reforms that would have weakened the ruling family.
This story originally appeared on Al Jazeera.
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