The authorities in Sudan arrested seven journalists as they covered economic protests there this week, including reporters for Reuters and Agence France-Presse, with no word on charges or when they might be released.

Press advocates said Friday that the arrests, carried out by Sudan’s National Intelligence and Security Service, reflected an increasingly repressive censorship in the vast African nation, where news media independence has long been under assault.

Security agents in the country have frequently confiscated newspapers in recent years and held journalists when their reporting displeased the government of the longtime president, Omar Hassan al-Bashir. The journalists are often released within hours, but not always.

The arrests this week were coupled with what press advocacy groups described as a government warning to Sudan newspapers to avoid reporting on the protests, which took place on Tuesday and Wednesday in the capital, Khartoum. Thousands marched peacefully to object to Sudan’s rapidly rising prices.