The violence which erupted in Mexico on Sunday is among the worst the country has known in years. Mexico's co-hosting of this summer's FIFA World Cup could be compromised by the eruption in drug cartel violence which began on Sunday, experts have told BBC Sport.

The Jalisco New Generation (CJNG) drug cartel - one of the country's most powerful and feared criminal organisations - has engaged in gun shootouts with the Mexican military, blocked roads, and burned vehicles in response to the killing of its leader Nemesio Oseguera Cervantes, better known as 'El Mencho', in an army operation. Violence began in the central-western Jalisco state - where a code red security situation has been declared - and has now spread to at least a dozen more regions, with videos posted online showing gunmen patrolling streets and smoke billowing over cities. At least 25 National Guard officers have been killed inside 24 hours.

Guadalajara, capital city of Jalisco and home to more than a million people, is scheduled to host four matches at this summer's tournament. Another five are scheduled in Mexico City, and four in Monterrey.

"When you push down on the cartels you do get pushback - the danger is that it can be very difficult to manage a security situation that spirals out of control," says Javier Eskauriatza, assistant professor of criminal law at the University of Nottingham.

The power vacuum created by El Mencho's killing could lead to a period of instability and further conflict as contenders vie to replace him. "In general, the cartels have an economic interest in making sure the World Cup is peaceful," Dr. Eskauriatza adds. "Yes, they pay off politicians and local police forces, but they also buy restaurants and own hotels. They are part of the economic system. It is useful for them if Brits, Americans, and others go to Mexico, spend their money and have a good time." BBC Sport has contacted FIFA for comment.

This video cannot be played Watch: Vehicles set ablaze across Mexico amid violence. The CJNG is estimated to be worth more than £10bn and has tens of thousands of members. It has been responsible for a series of massacres, kidnappings, and killings of politicians since its formation in 2009. But some cartel figures retain a level of popularity within local communities in Mexico, as they provide financing for local infrastructure and facilities.

"The response by the CJNG is, in a way, required by the rules of the game - if you have your leader nabbed, you have to respond, otherwise you look weak" says Dr. Eskauriatza. "They are not idiots - they know that social media will film and amplify these videos for them and they have made sure the response looks national."

The US government has advised Americans in Jalisco to shelter indoors until further notice, while fellow World Cup co-host nation Canada has cancelled flights to the Puerto Vallarta airport, and flight tracking apps showed many aeroplanes returning to their departure destinations around the world.

"In terms of tourists, I would say there will be a moderate risk for them", says Dr. Karina Garcia-Reyes, senior lecturer in criminology at UWE Bristol. "Unless more military operations are conducted this week, I would expect that the authorities in the most affected areas will be able to address potential risks, so overall I would expect tourists to be safe as long as they follow the authorities' indications."

This video cannot be played The effect violence in Mexico could have on the World Cup. Security planning for the World Cup has already been under scrutiny over the deployment of Immigration and Customs Enforcement (ICE) officers to major US cities by President Donald Trump, leading to the killings of two US citizens by federal agents so far this year, and a series of mass protests. Last month, Football Supporters Europe said it was "extremely concerned by the ongoing militarisation of police forces in the US". Now eyes are on Mexico and whether it can guarantee the safety of travelling fans.

Four football matches - two in the top flight and two in the second division - were postponed on Sunday because of the violence. "People in Mexico are hoping that this is a one-off retaliation and that as the cartel reorganises itself, things will settle down," says Monica Serrano Carreto, professor of international relations at El Colegio de Mexico. "But there is also a risk that this leads to a new period of instability, unpredictability and the violence continues."

"The type of weapons that the cartel has access to means that a military-style confrontation in the aftermath is inevitable - the government would have known that. We have seen in the past they [the cartel] even have weapons capable of shooting down helicopters. "I think it will already have had an impact on how people view coming to Mexico because the images are top of the news around the world."

Cartel members set alight transport infrastructure as well as banks, pharmacies and other local businesses. Mexico has been under increased political pressure to take action against cartels in the past year. "This response is not unique but is very serious and very high scale," says Jon Benjamin, UK ambassador to Mexico between 2021 and 2024. "President Trump has designated the cartels as terrorist organisations and Mexico has already handed over dozens of cartel figures to them. The Trump factor is very important in what is happening." Young Mexicans have been conducting a greater number of anti-cartel protests in major cities in recent years.