MEXICO CITY -- Mexican officials said Sunday they are pursuing all lines of investigation into the torture and killing of a photojournalist whose body was found in Mexico City, where he had fled because of harassment in his home state.

But the killings may have had to do more with the four women found dead alongside Ruben Espinosa, 31, who worked for the investigative magazine Proceso and other media, Mexico City prosecutor Rodolfo Rios Garza said in news conference.

Rios did not identify the other victims, only giving their ages as 18, 29, 32 and 40. He said they are focusing on the crime as a feminicide, though they have not discarded other motives.

Espinosa sustained severe injuries to his face before he was killed, said Dario Ramirez, director of the Article 19 free press advocacy group. Rios said all of the victims were shot in the head with a 9 mm weapon. They showed signs of resisting and had abrasions from fighting back.

Espinosa and the women were found dead late Friday in an apartment in a middle-class neighbourhood near central Mexico City. The women showed signs of sexual assault before being shot, Ramirez said. The building was in range of several security cameras on the street and Rios said they have video evidence in the crime, though he did not elaborate.

Ramirez said he urged prosecutors to make Espinosa's work the main line of investigation as a motive for his killing.

Article 19 had published an alert about Espinosa on June 15 after he reported unknown people following him, taking his photograph and harassing him outside his home in Xalapa, the capital of the Gulf coast state Veracruz, where 11 journalists have been killed just in current administration of Gov. Javier Duarte. Espinosa fled to Mexico City and sought protection on June 14, Ramirez said.

Rios in a news conference never acknowledged that Espinosa was seeking refuge, saying he came to Mexico City "seeking professional opportunities." Authorities in general in Mexico are quick to discard their work as a motive in journalist killings.

"I feel there is a disdain toward investigating the journalistic motives or even motives that had to do with his displacement," Ramirez told The Associated Press. "But the exact theme is that he was at risk and after a month he was assassinated. These are coincidences that can't be discarded by saying he was in the wrong place at the wrong time."

Veracruz has been a dangerous state for reporters. Espinosa is the second Veracruz journalist to be found dead outside of the state, along with 11 killed in Veracruz since 2010.

His killing has raised tension among reporters who long have considered Mexico's capital to be a refuge from media intimidation and violence elsewhere in Mexico.

"The level of impunity is what allowed this to happen," said a journalist in Mexico City who also had to flee Veracruz. "Displaced journalists used to come to Mexico City as an island of protection. Now there is no place to go, no place to run."

The journalist did not want to be named for security reasons.