A journalist has been murdered in a resort town on Mexico's Caribbean coast after receiving death threats, authorities said, the fifth reporter killed this year in one of the most dangerous countries for the press.

Francisco Romero, who was enrolled in the Mexican government's protection program for journalists and activists, was found dead outside a nightclub in Playa del Carmen, his hometown, according to prosecutors in the eastern state of Quintana Roo.

The state prosecutor's office opened a homicide investigation, saying Mr Romero had filed a complaint on 12 April over threats he had received.

Reporters Without Borders said the killing officially made Mexico the deadliest country in the world for journalists so far this year.

Last year, the watchdog group ranked the country the third most dangerous in the world for the press, after war-torn Afghanistan and Syria.

Mexico has been hit by a wave of violence linked to drug trafficking and political graft in recent years, and asking too many questions about crime or corruption can be a deadly business.

Across Mexico, more than 100 journalists have been murdered since 2000

Francisco Romero's wife, Veronica Rodriguez, said he had regularly received threats over his work, which sometimes rubbed local government officials the wrong way.

"He had received a lot of threats. Too many threats. The authorities in Mexico City knew about them," Ms Rodriguez told AFP.

Mr Rodriguez, who has three children would not say who had made the threats, saying she feared for her life.

Reporters Without Borders said Mr Romero had received a phone call at 5am informing him about some supposed news at a local night spot called the Gotta Gentleman Club.

Although he had four bodyguards provided by the government, he had sent them home at 10pm the night before, it said in a statement.

Mr Romero, who also had a panic button to alert the authorities if his life was in danger, went without them to the club. His body was found in the car park an hour later.

Mr Romero worked for one of the state's leading newspapers, Quintana Roo Hoy, and ran a Facebook-based news site called "Ocurrio Aqui" (It Happened Here) that covers local politics and crime and has more than 17,000 followers.

He had been under the official protection programme for journalists since 2018, according to Balbina Flores, Mexico director for Reporters Without Borders.

The government programme provides different kinds of security to threatened journalists and human rights activists, ranging from panic buttons to home surveillance to bodyguards.

Ms Flores said Mr Romero had been enrolled in it after the murder last year of one of his collaborators, fellow Playa del Carmen journalist Ruben Pat.

Four journalists have now been murdered in the state of Quintana Roo in the past year.

Across Mexico, more than 100 have been murdered since 2000. The vast majority of those killings remain unpunished.