The United Arab Emirates has formally designated the Muslim Brotherhood and local affiliates as terrorist groups, state news agency WAM reported on Saturday citing a cabinet decree.
The Gulf Arab state has also designated Nusra Front and the Islamic State, whose fighters are battling Syrian President Bashar al-Assad, as terrorist organisations, along with other Shi'ite militant groups such as the Houthi movement in Yemen.
Saturday's move echoes a similar move by Saudi Arabia in March and could increase pressure on Qatar whose backing for the group has sparked a row with fellow Gulf monarchies.
It also underscores concern in the U.S.-allied oil producer about political Islam and the influence of the Brotherhood, whose Sunni Islamist doctrines challenge the principle of dynastic rule.
The UAE has designated al-Islah group, which is a local Islamist group banned in the UAE for its alleged link to Egypt's Muslim Brotherhood, as a terrorist group.
UAE authorities have cracked down on members of al-Islah and jailed scores of Islamists convicted of forming an illegal branch of the Brotherhood. Al-Islah denies any such link, but says it shares some of the Brotherhood's Islamist ideology.
In an unprecedented public move, Saudi Arabia, Bahrain and the United Arab Emirates recalled their ambassadors to Qatar in March, accusing Doha of failing to abide by an agreement not to interfere in one another's internal affairs.
So far efforts by members of the GCC, an alliance that also includes Oman and Kuwait, to resolve the dispute have failed.
The three states mainly fell out with Qatar over the role of Islamists, including the Muslim Brotherhood. Gulf officials say the three want Qatar to end any support for the Brotherhood.
Qatar says it backs all Arabs, not just Brotherhood members.
Qatar's emir on Tuesday publicly invited fellow Gulf rulers to a Doha summit, apparently seeking to forestall what diplomats say is an attempt by some peers to move it elsewhere in protest at what they see as an Islamist tilt in his foreign policy.
