Mexico has demanded a full investigation¹ after a Mexican teenager died after apparently² being shot by a US border patrol agent.

墨西哥与美国边境一名少年被杀，墨西哥政府下令对此事进行全力调查，据悉该少年似乎是被一名美国边境巡逻警察枪杀。

The body was found on the Mexican side of the border

Mexican police said the youth was killed close to the bridge linking the border cities of El Paso and Ciudad Juarez.

The US border patrol said one of its agents had fired his weapon after stones were thrown at him.

The FBI says it is investigating the incident.

'Disproportionate force'

"We energetically condemn³（谴责） the death of a minor⁴ near the international border crossing in Ciudad Juarez", the Mexican foreign ministry⁵ said in a statement.

"Using firearms to respond to an attack with rocks is a disproportionate（不相称的） use of force, particularly coming from a officials that are specially⁶ trained," it said.

"A worrying increase in the use of excessive force" showed the need for greater cooperation on border security, it added.

The FBI said the agent opened fire during a confrontation⁷（对抗） with a group of suspected illegal aliens（非法入境者） trying to enter the US.

It said two people were arrested but the others retreated into Mexico, throwing rocks.

"The subjects surrounded the agent and continued to throw rocks at him. The agent then fired his service weapon several times, striking one subject who later died."

The boy has been identified as 14-year-old Sergio Adrian Hernandez.

Photographs show his body lying on the Mexican side of the Rio Grande.

His mother, Guadelupe Huereca, denied reports he had been trying to cross the border.

"He was not going to cross to El Paso, it is not true, he was here in Mexico. They killed him in Mexico," she said.

The issue of illegal migration⁸, and the treatment of Mexicans on the border, is a source of abiding⁹（持久的） tension between the United States and Mexico.

Last week Mexico made similar protests over the death of a Mexican migrant after he was given electric shocks by US agents who were trying to deport¹⁰ him.

There has also been anger in Mexico over a new law in the US state of Arizona, which requires police to question people about their immigration status, if officers suspect they are in the US illegally, and if they have stopped them for a legitimate¹¹ reason.

But in the US, there's substantial political support for stronger measures to stop the flow of illegal migrants across the Mexican border.

Mexicans make up three-quarters of the estimated 12 million illegal immigrants living in the US.