The US state department has warned tourists to "completely avoid" five states in Mexico because of rampant crime levels and gang activity.
Colima, Guerrero, Michoacán, Sinaloa and Tamaulipas have all been classified as a level-four risk, the highest in the scale.
That puts them at the same levels as conflict-ridden countries such as Afghanistan, Iraq and Syria.
Preliminary figures suggest that Mexico had a record number of murders in 2017.
Previously, the year with the most homicides had been 2011, when more than 27,000 people were killed according to official figures.
State department advice for travellers to Mexico:
- Use toll roads when possible and avoid driving at night
- Exercise increased caution when visiting local bars, nightclubs, and casinos
- Do not display signs of wealth, such as wearing expensive watches or jewellery
- Be extra vigilant when visiting banks or ATMs
- Have a contingency plan for emergency situations
The state department is concerned about violent crime in all of the five states but also warns of specific dangers in each one of them.
In the case of Tamaulipas, it says that gun battles are widespread and warn of travel by both public and private bus as armed criminal groups take passengers hostage and demand ransom payments.
"Local law enforcement has limited capability to respond to violence in many parts of the state," it says.
Sinaloa, where criminal gangs such as the Sinaloa cartel are active, is particularly dangerous.
The state department warns that "in Guerrero state, armed groups operate independently of the government in many areas". It adds: "Members of these groups frequently maintain roadblocks and may use violence towards travellers."
Its website also states that US government employees are prohibited from travelling to the entire state of Guerrero, including Acapulco.
The resort town was once a glamorous destination, but in recent years it has had one of the highest murder rates in the country.
While the state department is warning travellers to stay away from the five states categorised as level-four risk, Mexico as a whole is classified as a level two, where travellers should "exercise increased caution".