There is growing concern over the fate of the Burundian correspondent of German broadcaster Deutsche Welle (DW), who was arrested last week while reporting on Burundian refugees in the Democratic Republic of Congo (DRC).

Journalist Antediteste Niragira went missing after calling his wife on 20 May to say he was crossing the land border between Burundi and the DRC, where he was expecting to write a report on a refugee camp with many Burundian refugees at Lusenda, some 60 km inside the DRC.

According to information obtained by media campaign group Reporters Without Borders (RSF), Niragira was arrested by agents of the DRC's feared National Intelligence Agency (ANR) on the grounds that he did not have a visa.

Following his arrest near the town of Kavimvira, the journalist was transferred to a prison in Uvira, in the South Kivu Province.

Niragira has not been physically harmed, according to a lawyer commissioned by DW.

DW said Congolese authorities have refused to provide further information after they accused Niragira of being a spy, allegations DW spokesman Christoph Jumpelt described as "outrageous and baseless".

"We demand that the authorities in the DR Congo release Antediteste Niragira immediately and provide for his safe return to Burundi," Jumpelt said.

RSF also called for the journalist' immediate release. "There is no reason for Antediteste Niragira to be in prison. This journalist has broken no law. If the Congolese authorities don't want to let him into the DRC, they should release him so that he can return home," Cléa Kahn-Sriber, the head of RSF's Africa desk, said.

Reporters in the DRC are facing repeated threats and violence in the volatile African nation that is now ranked 154nd out of 180 countries in the latest World Press Freedom Index published by RSF.