The front pages of major newspapers and journalists demonstrating in the center of the capital carried pictures of Javier Valdez, 50, who was shot dead in broad daylight on Monday in northwestern Sinaloa state.
The awarding-winning Valdez was one of the most prominent reporters on Mexico's deadly drug war. He had been a contributor to AFP for more than a decade.
President Enrique Pena Nieto said he had ordered "an investigation of this outrageous crime." He vowed to defend press freedom, "fundamental for our democracy."
Press rights group Articulo 19 said that was the first time Pena Nieto had reacted publicly to one of the recent wave of journalists' killings - a sign of rising pressure on the president.
But the killing fanned a wave of anger at the authorities, with rights groups saying corrupt officials are preventing journalists' killers from being punished.
The Mexican journalists' message that reads in Spanish 'In Mexico they are killing us' at Angel de la Independencia on May 16, 2017 in Mexico City, Mexico. (Getty) Source: LatinContent Editorial
"How long will there be killings without pity and with impunity?" said Valdez's own weekly publication, Riodoce.
"Murderous impunity," ran the headline of an editorial in La Jornada, the national daily for which Valdez worked as Sinaloa correspondent.
Valdez was due to be cremated at 2300 GMT on Tuesday, his family said.
'Brazen' killings
Journalists' unions said they planned demonstrations in homage to Valdez, including one outside government headquarters in Mexico City and one in his home town of Culiacan, where he was shot.
Some media in Sinaloa canceled their Tuesday editions in protest.
"This wave of violence shows the state of emergency in which Mexican journalists are living," said Emmanuel Colombie, Latin American director of Reporters Without Borders.
"The Mexican government must take action proportionate to the seriousness of the situation and strengthen protection for journalists as soon as possible."
Numerous media and human rights organisations including Amnesty International called for an impartial investigation.
They accused the authorities of failing to prosecute those who kill journalists covering the drug gangs in broad daylight, sometimes in front of their families.
Journalists show pictures of Mexican journalist Javier Valdez, murdered on the eve, during a protest by journalists in Mexico City on May 16, 2017. (Getty) Source: AFP
"It has become brazen and cynical," said Ana Cristina Ruelas, Mexico director of Articulo 19, a group that defends press freedoms.
"The state is not capable of investigating properly and that is an inducement for them to keep killing journalists."
Articulo 19 says 105 journalists have been murdered and a further 23 have disappeared since 2000.
Of those cases, 99.7 percent remain unsolved, meaning the culprits have gone unpunished, it says.
Risking his life
Valdez had written extensively for Mexican newspapers.
"Being a journalist is like being on a black list," he wrote in a recent book about drug gangs and the media.
"Even though you may have bulletproofing and bodyguards, (the gangs) will decide what day they are going to kill you."
His last contribution to AFP was 11 days ago, about the extradition to the United States of Joaquin "El Chapo" Guzman, former head of the notorious Sinaloa cartel.
Valdez's brother Rafael said the reporter had been "very happy" in recent days and had not indicated having received threats.
"He was very reserved when it came to his work. He never talked about it so as not to drag people into it," Rafael Valdez told AFP.
"I asked him why he risked his life (for his work) and he replied: 'It is something I like doing, and someone has to do it. You have to fight to change things.'"
Mexico ranks third in the world for the number of journalists killed, after Syria and Afghanistan, according to media rights group Reporters Without Borders (RSF).
