A human rights group in Democratic Republic of Congo (DRC) has criticised the government for blocking the signal of a popular foreign radio station.

The signal of Radio France Internationale (RFI), one of the most popular stations in the DRC, has been blocked since Saturday when an opposition protest against the government in Kinshasa was due to take place.

Authorities in the DRC had banned the rally and police were out in force to prevent protesters against president Joseph Kabila from gathering.

La Voix des sans-voix (VSV -- the voice of the voiceless) said in a statement it "condemns the umpteenth blockage of the Radio France Internationale signal by the Congolese government".

VSV described the blocking as an "inadmissable attack on freedom of the press" in the country.

As well as demanding the immediate unblocking of Paris-based RFI's signal, it also called for the frequency of United Nations-backed Radio Okapi to be unscrambled.

The station has been blocked since Saturday.

"We are disappointed with what has happened to Radio Okapi but also RFI," Antoine-Charles Bambara, the UN's director of public information in DRC, told AFP.

Kabila's government has frequently interfered with RFI broadcasts over the last two years -- blocking transmissions any time opposition supporters have organised protests against the president.

Government spokesman Lambert Mende declined to comment.

VSV accused the government of seeking to keep Congo's people "in darkness and ignorance concerning the management of public affairs".

The weekend protests were called by Etienne Tshisekedi, leader of the main opposition group, to insist that Kabila must step aside in December when his term ends.

Kabila has been in power since 2001.

A deal was reached last month between Kabila's government and a fringe opposition group allowing him to remain in power until April 2018.

In September, 49 people were killed in violence sparked by anti-Kabila demonstrations.

Kabila took power in 2001, 10 days after the assassination of his father, the then-president, Laurent Kabila.

Jospeh Kabila was first elected to a five-year term as president in 2006. He then won a hotly-disputed election against Tshisekedi in 2011 -- the second and final time he was eligible to stand.

The country has been in political crisis and suffered from sporadic outbreaks of violence ever since.

While RFI remains blocked in DRC, inhabitants can still receive the station's signal from neighbouring Republic of the Congo.