A 4-year-old boy was killed by gunmen while he was playing outside a neighbor's house in Ciudad Juarez, considered Mexico's murder capital and the most dangerous city in the world, police said.

Alan David Carrillo was playing with a friend when a group of gunmen opened fire on the house, the Ciudad Juarez municipal police department said in a statement.

The boy's relatives rushed him to a clinic, but he died a few minutes after arrival at the medical facility.

Ciudad Juarez, located across the Rio Grande from El Paso, Texas, has been plagued by drug-related violence for years.

The murder rate took off in the gritty border city of 1.5 million people in 2007, when 310 people were killed, then it more than tripled to 1,607 in 2008, according to Chihuahua state Attorney General's Office figures, with the number of killings climbing to 2,754 in 2009.

More than 3,100 people were murdered in the border city last year, making 2010 the worst year since a war between rival drug gangs sent the homicide rate skyrocketing in 2008.

The killing has not slowed this year, with nearly 1,900 people murdered in Juarez, the state AG's office said.

The violence is blamed on a war for control of the border city being waged by the Juarez and Sinaloa cartels with backing from hitmen from local street gangs.