Yaounde, Cameroon - Authorities in Cameroon say 27 people, including senior police officers and a well-known media mogul, have been detained in connection with the killing last month of popular journalist Martinez Zogo.

Journalists in Cameroon say they are increasingly receiving death threats and experiencing harassment. The media professionals called for justice and protections after two journalists who reported on corruption were found dead in the capital in two weeks.

The mutilated body of radio host Zogo was found on January 22 in Yaounde, five days after he was abducted. On February 2, Jean Jacques Ola Bebe, a Catholic priest and radio host, was also found dead in the capital.

Two days earlier, Bebe, who had called for justice for Zogo, told Cameroon's Galaxy FM Radio he was receiving regular death threats that he suspected were from authorities.

The president of the Cameroon Journalists Trade Union, Marion Obam, told local media Tuesday at a press conference in Douala that Cameroonian journalists will wear dark clothes every Wednesday to show they want all suspected killers of journalists arrested and brought to justice. She said in the past four years, four journalists have either been killed or have died in suspicious circumstances, while at least 20 experienced severe violations of their rights.

The president's office on Friday said more than 20 people had been detained over Zogo's killing, including senior police intelligence officers.

The statement did not elaborate and officials declined requests for comment.

On Monday, police detained seven more people, including media mogul Jean-Pierre Amougou Belinga at his Yaounde home.

They also detained Belinga's chief of security, who is a former presidential guard commander, and the head of his Vision 4 TV channel.

It's not clear if anyone has been officially arrested or charged.

Zogo, on his radio program, said Belinga had plans to kill him for reporting on Belinga's alleged corrupt deals with officials.

Authorities in Cameroon have not issued a statement on the killing of Bebe.

Government spokesman Rene Emmanuel Sadi told state Cameroon Radio Television on Sunday authorities will punish anyone involved in killing or threatening journalists.

He said Cameroon is a country of laws where fundamental freedoms, including press freedoms, are guaranteed by the state. Sadi urged all Cameroonians, especially journalists, to wait for the results of investigations ordered by President Paul Biya into the murder of Zogo and other abuses.

Since the killings, several other journalists in Cameroon say they have received death threats.

Police have detained reporters who interviewed colleagues of the journalists who were killed, allegedly seizing their equipment and erasing their recordings.

Yaounde-based freelance reporter Fonban Emmanuel told VOA on Tuesday the atmosphere for the press is one of intimidation and fear.

'Nobody would want to be killed. When journalists are moving, they feel that the worst can come to them. We even have some families who are already beginning to advise that their children should not engage in journalism because it could invite agony to their lives,' Fonban said. 'Many journalists are waiting to see the Cameroonian government bring to book those who have brought this kind of agony to the media in Cameroon.'

The U.N.'s human rights spokesperson in Geneva issued a statement Tuesday of deep concern over the second killing of a journalist in Cameroon in two weeks and called on authorities to ensure an independent, effective and impartial investigation.

The Committee to Protect Journalists has called on Cameroonian authorities to ensure transparency in the investigations and deliver justice.