MEXICO CITY -- Homicide cases in Mexico rose by 15 per cent in 2018, law enforcement agencies reported this week.

Government figures show prosecutors opened 28,816 investigations in 2018, compared to 25,036 the previous year.

Each case may involve more than one victim, so the total number of homicides is likely to be higher.

The increase was led by dramatic rises in violence in parts of the country like the Caribbean coast state of Quintana Roo, where homicide cases more than doubled. The state, where the resort of Cancun is located, saw 763 homicide cases in 2018, compared to 359 in 2017.

On Sunday, three gunmen in Cancun shot seven people to death at a home in an apparent dispute between street-level drug dealers. State authorities said a suspected gang leader who has been linked to the Jalisco cartel was behind the killings. The cartel from the Pacific coast has been trying to take over illegal activities in Cancun and resorts to the south.

Another state where homicide cases more than doubled was Guanajuato, located northwest of Mexico City. Guanajuato was once a largely peaceful farming and industrial state, but in 2018 there were 2,609 cases, compared to 1,084 in 2017. Authorities attribute the increase to the rise of fuel-theft gangs who frequently fight their rivals.

Some previously violent Mexican states have managed to reduce the number of homicides.

Baja California Sur, the state where the resorts of Los Cabos are located, suffered through a bloody year in 2017, as drug gang battles boosted the number of homicide cases to 610; but that number fell to 244 in 2018.

The Gulf coast state of Veracruz cut homicides by 20 per cent.