In December 2012, newly installed President Enrique Pena Nieto promised to switch the focus of Mexico's drug wars from tackling the gang leaders to reducing the crime and violence that affect the lives of Mexicans.

What is the scale of the violence?

Official figures have been issued only sporadically. Most estimates put the number of people killed in drug-related violence since late 2006 at more than 60,000. Although there is no official breakdown of the numbers, the victims include suspected drug gang members, members of the security forces and those considered innocent bystanders. Analysts tracked an overall decline in violence during 2012, continuing a trend from the previous year.

Where are the worst-hit areas?

Violence was first concentrated in the northern border regions, especially Chihuahua, as well as Pacific states like Sinaloa, Michoacan and Guerrero. Ciudad Juarez, just across from El Paso in Texas, was the most violent city. In 2010, some 3,100 people were killed in Juarez, which has a population of about one million. Violence has now dropped markedly in Juarez.

Guerrero, home to the resort of Acapulco, Sinaloa and Nuevo Leon remain among the most violent regions. One of the focal points of violence since 2010 has been Mexico's third-largest city, Monterrey, which became the centre of a turf war between the Zetas and Gulf cartels. Veracruz on the eastern coast saw a series of mass killings in 2011 after previously being largely untouched by the violence.

Who are Mexico's powerful cartels?

The cartels control the trafficking of drugs from South America to the US, a business that is worth an estimated $13bn a year. Their power grew as the US stepped up anti-narcotics operations in the Caribbean and Florida. A US state department report estimated that as much as 90% of all cocaine consumed in the US comes via Mexico.

Alliances shift between the main gangs as they vie for control of trafficking routes. For several years the two main players were the Sinaloa (also known as the Pacific) cartel and the Zetas. US security firm Stratfor said in a January 2012 report that the Zetas were the biggest cartel in terms of geographic presence.

But since then the Zetas have been ravaged by infighting and splits, and the leaders of both main factions have now been eliminated. Miguel Angel Trevino Morales was captured in July 2013 and Heriberto Lazcano was killed by marines in October 2012.

What has been Mexico's strategy to tackle drug-trafficking and violence?

The government's efforts have for years been undermined by corruption by members of the security forces who collude with the gangs.

Former President Felipe Calderon deployed more than 50,000 troops and federal police against the cartels. Many of the main gang leaders were either arrested or killed. However, the violence soared under his administration.

His successor, Enrique Pena Nieto, has promised a lower-profile approach aimed at tackling the violence on a local level by setting up of a national gendarmerie to take over from the troops. The federal police will also be boosted to focus on investigations.

What has been the US response to the drug trafficking and violence?

In March 2009, the US government announced that it would step up efforts to disrupt the illegal flow of weapons and drug profits from the US to Mexico - a key demand of the Mexican government.

However, in November 2010, a US justice department report said that US efforts to tackle gun-smuggling lacked focus, with not enough intelligence-sharing between US agencies and with their Mexican partners.

And a Senate report in June 2011 suggested that some 70% of firearms recovered from Mexican crime scenes in 2009 and 2010 and submitted for tracing came from the US.