Mexican authorities on Sunday arrested a former police officer in connection with the brutal slaying of a prominent photojournalist and four others in a case that sparked international outrage.

Police arrested a man "identified as Abraham Torres Tranquilino" for alleged involvement in the killing of Ruben Espinosa, rights activist Nadia Vera and three other female victims, Mexico City prosecutor Rodolfo Rios said in a statement.

Espinosa and the other victims were found dead on July 31 this year in a Mexico City apartment, their hands bound and their bodies bearing signs of torture.

Torres, 24, worked as a police officer in the capital until 2011, when he was arrested and convicted of torture in a separate case. He went on to serve about a year in jail.

Authorities on August 4 arrested Daniel Pacheco Gutierrez, also an ex-convict, in the latest case.

He said he was innocent but acknowledged being in the apartment where the killings occurred, along with two other friends, the day the murder happened.
Prosecutors weeks ago released security footage of Pacheco and Torres leaving the building the day of the murder along with another man.

Espinosa's death was the latest in a string of journalist slayings that prompted a group of hundreds of leading intellectuals from Mexico and around the world to call on Mexican President Enrique Pena Nieto to better protect the press.

The group included Britain's Salman Rushdie, American Paul Auster and Canada's Margaret Atwood.

Across Mexico, at least 89 journalists have been murdered since 2000, according to Reporters Without Borders, and another 20 or so have disappeared.

Pena Nieto on August 19 pledged to beef up the protection of reporters and human rights advocates.