* Saudi designation of Brotherhood divides Gulf Arab bloc * Uncertainty over impact on Brotherhood supporters * Islamist groups part of politics in Kuwait, Bahrain By Yara Bayoumy and Sylvia Westall DUBAI/KUWAIT, March 12 (Reuters) - Saudi Arabia's fierce campaign against the Muslim Brotherhood, already on the run in its Egyptian birthplace, has divided a Gulf Arab bloc, causing discomfort in some member states where the Islamist group is embedded in daily politics. Feuding with Qatar over Islam's place in a turbulent Arab world, Riyadh recalled its ambassador from Doha last week and branded the Brotherhood, a Qatari ally, a terrorist group. Saudi Arabia has swung firmly behind the Egyptian military, which deposed President Mohamed Mursi last year after mass protests against the Brotherhood leader.