|More than 28,000 people have died in drug violence since war was declared on cartels in late 2006 [AFP]
Following is a timeline of important events in the war on drugs in Mexico, a major transit point for narcotics smuggled into the United States:
2001 - Joaquin "Shorty" Guzman escapes from a Mexican prison in a laundry van. Mexico's most-wanted drug lord, he builds a coalition of drug gangs from the western state of Sinaloa and vows to take control of Mexico's vast drug trade.
2002 - Police weaken the Tijuana cartel by killing Ramon Arellano Felix, a drug boss, and arresting one of his brothers.
2003 - Mexican soldiers capture Osiel Cardenas, leader of the Gulf cartel based in eastern Mexico, after a shootout between troops and armed men in the border city of Matamoros.
2004 - Trying to take advantage of Cardenas' arrest, Guzman sends well-armed enforcers to border cities south of Texas to take over Gulf cartel-smuggling routes. Heavy fighting breaks out before Guzman's fighters are eventually repelled.
2005 - Guzman seeks control of the border city of Tijuana and trafficking routes into California. Violence escalates across Mexico and about 1,500 people are killed over the year.
2006 - Killings spread to the resort of Acapulco, the industrial city of Monterrey, and to Michoacan in western Mexico, the home state of Felipe Calderon, the Mexican president. After taking office on December 1, Calderon immediately sends out troops and federal police to stem the violence.
Drug gang killings rise to 2,300 and beheadings, torture and other atrocities increase.
2007 - Calderon extradites Cardenas to the US and makes a historic 23-tonne cocaine seizure. George Bush, the then US president, pledges $1.4bn in drug-fighting gear and training for Mexico and Central America. Violence escalates and more than 3,000 people are killed over the course of the year.
2008 - Guzman's fighters take on the Juarez cartel in the northern border city of Ciudad Juarez, across from El Paso, Texas, which quickly becomes the drug war's bloodiest flashpoint.
Drug violence kills around 6,300 people across Mexico over the year.
2009 - Calderon sends 10,000 more troops to Ciudad Juarez but the killings continue. Violence spills over the border into Arizona. Barack Obama, the US president, visits Mexico and vows to clamp down on smuggled guns but the annual drug war death toll soars above 7,000.
In December, an elite navy team tracks down and kills drug lord Arturo Beltran Leyva, head of the cartel of the same name and one of Mexico's most-wanted traffickers. Six bodyguards also die in the raid on a luxury apartment in the city of Cuernavaca near the capital.
2010 - In January police capture Teodoro "El Teo" Garcia Simental, drug kingpin, known for having rivals tortured, killed and then dissolved in acid.
But the cartels grow more brazen, killing three people linked to the US consulate in Ciudad Juarez, murdering a governors' election candidate in the increasingly lawless northeastern state of Tamaulipas and setting off car bombs. Mass killings at drug-rehabilitation centres and parties become common and mayors and local officials are assassinated.
In late July, Ignacio "Nacho" Coronel, ranked third in Guzman's Sinaloa cartel, dies as soldiers try to arrest him near Guadalajara.
The following month, Mexican troops find 72 bodies of illegal migrants at a remote ranch near the US border - the biggest single discovery of massacre victims since the launch of the so-called drug war.
On August 30, in Calderon's second coup of the year, authorities capture Edgar "La Barbie" Valdez, the US-born trafficker who was fighting to lead the Beltran Leyva gang based in central Mexico. Valdez was said to put up little resistance when he was captured in the state of Mexico.
Drug gang violence, however, has continued with three mayors being killed in different parts of the country between August and September.