Saudi Arabia has designated the Muslim Brotherhood a terrorist organisation as it escalates its crackdown on local jihadists.

A Ministry of Interior statement issued on 7 March announced that Riyadh had designated the Muslim Brotherhood and two other jihadist groups fighting with the Syrian rebels – the Nusra Front and the Islamic State in Iraq and the Levant – as terrorist groups.

The statement also gave Saudis fighting in Syria 15 days to return home. It follows a royal decree issued in February that stated that any citizen found guilty of fighting in conflicts abroad faced a jail sentence.

Hundreds of Saudis are reported to be fighting in Syria and analysts say Riyadh fears they could pose a security risk when they return home.

Although the kingdom has supported the Sunni-led rebels fighting to overthrow Syrian President Bashar al-Assad, it has long feared a backlash from radical jihadist groups.

Last month, King Abdullah decreed jail terms of up to 20 years for anyone belonging to “terrorist groups” or fighting abroad. The new law also promised tough sanctions for anyone backing the incriminated organisations.

The latest development is also set to escalate tensions between Riyadh and Doha. Earlier this week, Saudi Arabia, UAE and Bahrain withdrew their ambassadors from Doha, for its support of the Muslim Brotherhood in Egypt.

The Muslim Brotherhood is already banned in Saudi Arabia.