The Guatemalan army has announced it is sending 3.000 soldiers to its border with Belize after the Belizean army killed a 13-year-old boy.

Defense Minister Williams Mansilla, who announced the deployment of elite soldiers from the Kaibil base in northern Guatemala on Thursday, said it was a "dissuasive measure in order to avoid these kind of lamentable incidents."

Belize's government has disputed the claim that the soldiers attacked the boy. It insists that the incident was provoked when a Belizean patrol came under fire.

"Belizean security forces and law enforcement officials would never perpetrate an armed attack on civilians, especially minors, except in exercise of the right to self defence," read a statement issued by the office of Prime Minister Dean Barrow.

This exchange of accusations follows a period of rising bilateral tension that began with the landslide victory of former TV comedian Jimmy Morales in Guatemala's presidential elections last October. Morales has ties to hardline sectors in the military that have long insisted Guatemala should step up the pursuit of its claims to almost half of Belizean territory.

The Guatemalan authorities say Julio Alvarado Ruano was working on the small family farm in the northern department of Petén when he was shot dead by Belizean soldiers who also injured his father and his 11-year-old brother. The boy's corpse is in Belizean territory while his brother and father are in Guatemala.

Speaking to reporters in New York on Friday, President Morales called the incident "a cowardly and excessive attack."

"What possible threat can two children represent to their sovereignty," he said. "This act causes indignation and repudiation."

On Thursday, the Guatemalan foreign ministry released a statement it which it accused the Belize's security forces of killing 10 Guatemalan farmers since 1999 and then, rather than punishing the officers involved, "decorating them like heroes."

For its part, the statement from the office of Prime Minister Barrow, accused the Guatemalans of killing two police officers in "earlier incidents."

"The latest shooting attack on Belizean officials is part of a continued pattern of aggression by Guatemalan civilians engaged in illegal activities on the Belize side," the statement said.

With little sign of either side toning down the rhetoric, the Organization of American States released a statement on Friday condemning the killing of the boy, and urging both sides to find a peaceful way out of the situation.

"The OAS General Secretariat calls on the government of Belize and Guatemala to avoid an escalation of tensions and to renew their efforts to establish a lasting peace," the statement said.

The statement also promised that the OAS will carry out an investigation into what really happened.