Burundi has banned the U.K. public broadcaster BBC and indefinitely suspended Voice of America, moves that campaigners and the international broadcasters described as a blow to press freedom.

The central African nation's media regulator National Communications Council (CNC) revoked the BBC's license and accused it of airing a documentary that it said was false and damaged the country's reputation. It extended an existing suspension on VOA, because the broadcaster worked with radio journalist Patrick Nduwimana, who the government accuses of having taken part in a failed coup in May 2015.

The broadcasts, in Burundi's Kirundi language as well as in French and English, had been a popular news source across the country.

Both broadcasters were suspended, initially for six months, in May last year in the run-up to a referendum that opposition politicians and activists said was designed to extend the president's rule for at least a decade. At the time it accused both of breaching press laws and unprofessional conduct. They have been off air in Burundi ever since.

Media regulators warned against journalists supplying either the BBC or VOA with news.

"It is strictly prohibited for any Burundian journalist or foreign national who are in the country to provide, directly or indirectly, information that can be broadcast" by the BBC or the VOA, the CNC said.

"The unwarranted decision of the Burundi government to ban the BBC and suspend indefinitely Voice of America strikes a serious blow against media freedom, and we strongly condemn it," the BBC said in a statement.

"We believe it is vital for people around the world to have access to impartial, accurate and independent journalism, including the 1.3 million people in Burundi who currently rely on BBC news."

The publicly funded British broadcaster aired a documentary last year about what it said were secret detention and torture sites in Burundi. The government dismissed the report and the BBC said it stood by its journalism.

"We are alarmed that reporters in Burundi are now forbidden to communicate with VOA and believe these continuing threats to our journalists undermine press freedom in the country," VOA Director Amanda Bennett said.

BBC and VOA broadcasts continue on short wave frequencies, which can be listened to inside the country by anyone with the necessary radio.

Hundreds of Burundians have been killed in clashes with security forces and half a million have fled abroad since President Pierre Nkurunziza announced in 2015 he would run for a third term in what his opponents saw as a breach of the constitution. He won re-election.

The violence has claimed at least 1,200 lives and displaced more than 400,000 people between April 2015 and May 2017, according to estimates by the International Criminal Court (ICC), which has opened an investigation.

Last May's referendum overwhelmingly approved changes that could let the president stay in power to 2034 - though the opposition rejected the results and the United States said the process had been marred by voter intimidation.

Burundi ranks 159th out of 180 countries on the World Press Freedom Index 2018, compiled by the advocacy group Reporters Without Borders. Burundi has denied that there are widespread restrictions.

"The withdrawal of the BBC's operating license and continued suspension of the VOA are further brazen efforts by the Burundian authorities to silence the media," Amnesty International's Sarah Jackson said in a statement.

In 2018, the government also ordered the U.N. human rights office to close its bureau in the country, after it published negative reports on the situation in the country.

Meanwhile, Burundi on Friday released the first 142 prisoners from a promised 3,000 detainees to promote reconciliation, the justice minister said, but critics said it was only to ease pressure on crowded jails.

Justice Minister Aimee-Laurentine Kanyana attended a release ceremony in the prison at Gitega, the new official political capital of the small east African nation, for the first batch of released prisoners.

Nkurunziza promised the prisoner releases in December 2018, the third time he has granted mass pardons to prisoners since the country spiraled into crisis in 2015, sparking mass arrests.

The government has said the releases are to promote "national reconciliation". But opposition and civil society groups in exile say no political prisoners are to be released and that the move is just to free up more space in jail.

Prisons are massively overcrowded. Burundi has 11 prisons with a capacity for some 4,000 prisoners, but are currently housing more than 11,000 people, according to the rights group Aprodeh.

Those earmarked for release are serving sentences for relatively petty crimes.

"This decree... unfortunately excludes some 4,000 political prisoners who languish in Burundian prisons," said Aprodeh director Pierre-Claver Mbonimpa.