A man directs an airplane carrying wounded Yemenis, transported to Sudan to receive treatment in Sudan hospitals, at Khartoum airport, Sudan September 5, 2015.

Sudanese security agents have blocked four civil society representatives from attending a meeting with diplomats in Geneva about human rights in Sudan, a coalition of rights groups said on Friday.

The meeting in Geneva on Thursday was organized by an international NGO ahead of a United Nations-led review of the human rights situation in Sudan.

“Four representatives of Sudanese civil society were intercepted by security officials at Khartoum International Airport on their way to a high level human rights meeting with diplomats which took place in Geneva on 31 March,” the International Federation for Human Rights (FIDH) said in a joint statement with 35 international and Sudanese rights groups.

Agents from Sudan’s National Intelligence and Security Service (NISS) stopped the individuals as they tried to travel from Khartoum to Geneva via different routes between March 23 and March 28 and confiscated their passports, the statement said.

The four were named as lawyers Salih Mahmoud Osman, professor Muawia Shaddad, civil society activist Sawsan Elshowaya, and head of the Sudanese Solidarity Committee Siddig Yousif.

NISS gave no reason for the travel bans and the rights groups urged the security services to return the passports.

“The recent flagrant actions of the NISS are symptomatic of a broader strategy to intimidate and harass human rights defenders and independent civil society actors who may be critical of the human rights situation in the country,” the statement said.

Sudan’s security forces have been accused of harassing and detaining rights activists, opposition politicians and journalists.

The country regularly ranks near the bottom of international human rights indexes.

President Omar al-Bashir is also wanted by the International Criminal Court on charges of war crimes, crimes against humanity and genocide related to the conflict in the western Darfur region.

Bashir denies all charges by the ICC.

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