Sudan shut down a leading pro-democracy think-tank on Monday, a day after the organization helped stage a protest against government crackdowns on campaigners, its director said.
The Al-Khatim Adlan Center for Enlightenment and Human Development (KACE) was one of a number of bodies that tried to deliver a petition to the country's human rights commission on Sunday.
Police armed with batons blocked their way and, on Monday, a government official told the organization its operating license had been withdrawn, director Bakr Afif told Reuters.
Sudan has avoided the mass "Arab Spring'' uprisings that unseated rulers in neighboring Egypt and Libya.
But authorities have clamped down on a series of small protests over corruption, rising prices and austerity measures imposed to cope with an economic crisis exacerbated by the secession of the country's oil-producing south last year.
"We were informed today by the Humanitarian Aid Commission (HAC) that we have to close and that our license has been annulled,'' said Afif, referring to the government body that licenses non-governmental groups.
Security agents later took documents and other property, witnesses said.
KACE, one of Sudan's biggest civil society organizations, held workshops promoting democracy and the rule of law and said it was working to establish "long-term peace and stability in Sudan'' on its website.
It had helped draft the protest petition that gave details of alleged cases where the government had hampered the work of other groups.
A source at HAC declined to comment, saying a separate state body was responsible for the closure. The source added KACE could appeal against the decision.
No one was immediately available to comment from Sudan's security service.
Police fired teargas at university students in early December after four days of protests following the death of four students from Sudan's strife-torn Darfur.
The demonstrations were the most sustained to hit Sudan since a wave of small protests against government austerity measures in June.