At least 11 people were killed and another dozen injured when gunmen opened fire on locals who had gathered at a football pitch in the city of Salamanca in central Mexico on Sunday.
Witnesses said armed men arrived at the grounds in several vehicles and shot at those gathered there seemingly indiscriminately.
Many families had stayed behind to socialise after a match between local clubs. At least one woman and one child were among those killed.
The motive behind the shooting is not yet clear. Guanajuato, the state in which Salamanca is located, registered the highest number of murders in the whole of Mexico last year.
Neighbours reported hearing at least 100 shots ring out as the gunmen opened fire at the Cabañas pitch in the Loma de Flores neighbourhood.
Local and federal security forces are now investigating the deadly shooting.
It came just a day after several violent incidents in the city, in which a total of five men were killed and another was abducted.
Guanajuato has seen a spike in violence committed by a number of gangs that engage in the theft of oil and fuel, as well as other criminal activities such as drug trafficking and extortion.
Gang members frequently hold up tanker trucks carrying oil and tap oil pipelines belonging to state-run oil company Pemex.
Salamanca, which is home to a major Pemex refinery, has been particularly subject to violent gang-related attacks.
Analysts say that the rivalry between the Jalisco New Generation Cartel (CJNG) and the Cartel de Santa Rosa de Lima (CSRL) is behind many of the most brutal incidents.
Their criminal activities are not confined to Mexico, with both the smuggling of stolen fuel and illicit drugs spreading violence into the United States.
Last year, the US State Department designated the CJNG as a Foreign Terrorist Organisation and, more recently, placed sanctions on the CSRL.
US President Donald Trump has made the fight against criminal gangs sending illicit drugs such as heroin, fentanyl, methamphetamines and cocaine one of his priorities.
He has in the past alleged that “cartels are running Mexico” and has threatened to hit “narco-terrorists” with land strikes.
The US has already carried out at least 36 strikes against vessels allegedly transporting drugs by sea, both in the Caribbean and the Pacific, killing at least 125 people.
Legal experts and Trump’s critics have questioned the legality of these strikes.
Mexican President Claudia Sheinbaum last week handed over 37 “high-impact” suspects to the US in what local media described as an attempt by her government to co-operate with US counternarcotic efforts and thereby ward off the possibility of Trump ordering unilateral strikes against the cartels in Mexican territory.
