Saudi Arabia listed Friday the Muslim Brotherhood of deposed Egyptian president Mohamed Morsi as a terrorist organisation, along with Syria's two main militant groups, according to Al-Arabiya television network.
The two groups are Al-Nusra Front, which is Al-Qaeda's official Syrian affiliate, and the Islamic State of Iraq and the Levant (ISIL), a rogue group fighting in both Syria and Iraq.
Yemen's Shia Huthi rebels and the Saudi Hezbollah were also included in the official decree.
The decision follows an unprecedented diplomatic act on Thursday by Saudi Arabia, Bahrain and the UAE to withdraw their ambassadors from Qatar, expressing rejection to the latter's pro-Brotherhood orientation in its foreign policy.
On 3 February, Saudi’s King Abdullah issued a decree that punishes citizens who fight in conflicts outside the Gulf kingdom with sentences ranging from 3 to 20 years in jail.
The statement issued by the Saudi Royal Court also stated that any Saudi citizens who joins extremist terrorist groups or supports them materially or through incitement would face an even harsher punishment ranging from 5 to 30 years in jail.
According to the Associated Press, the step seems to target the flow of Saudi fighters going to Syria to join the uprising there.
Egypt's interim government officially declared the Muslim Brotherhood a terrorist group last December, making it subject to Article 86 of the Egyptian penal code, which defines terrorism and the penalties for engaging in it.