WASHINGTON -- Two legal rights groups on Thursday asked the United Nations to investigate allegations that Spanish and U.S. officials collaborated to quash criminal probes into whether the Bush administration authorized illegal killings and torture of terrorism suspects.

The request, made to the U.N.’s special rapporteur for judicial independence, accused the United States of interfering with Spain’s justice system in three different criminal cases. The New York-based Center for Constitutional Rights and the Berlin-based European Center for Constitutional and Human Rights asked that the U.N. demand that both governments refrain from meddling in court cases.

“When arguably the leading human rights country in the world is engaged in torture and then gives impunity to those torturers, it sends a pretty bad message,” said Michael Ratner, the Center for Constitutional Rights’ president emeritus.

Ratner said the groups were turning to the U.N. because “it’s very hard to hold the U.S. accountable in any forum in the world.”

A spokesman for the U.S. State Department declined to comment, referring questions to the Justice Department, which did not respond to requests for comment.

The complaint calls for the U.N. to investigate how three cases were handled. The first involved the alleged torture of detainees at the U.S. detention center at Guantánamo Bay, Cuba; the second, the Bush’s administration’s authorization of harsh interrogation techniques; and the third, the 2003 death of Spanish cameraman Jose Couso Permuy in Baghdad.

The two groups based their complaint on diplomatic cables published by WikiLeaks in 2010 that recount high-ranking U.S. diplomats pressuring Spanish officials to stop the investigations.

In one, U.S. Ambassador Eduardo Aguirre recounts his efforts to prevent criminal charges in the death of Couso, who was killed during the U.S. capture of Baghdad on April 8, 2003, when a U.S. tank opened fire on the Palestine Hotel, where journalists were staying.

“While we are careful to show our respect for the tragic death of Couso and for the independence of the Spanish judicial system, behind the scenes we have fought tooth and nail to make the charges disappear,” Aguirre wrote.

On Friday, a Spanish judge reopened the case of the four former Guantánamo captives who allege they were tortured and subjected to humiliation at the detention camp. The judge ruled that he had jurisdiction in the case because the United States was not conducting an independent probe of the allegations.

“We’re very excited about these cases in Spain,” Ratner said. “It’s only happening because neither the Bush administration nor the Obama administration is willing to do anything to investigate the torture at Guantánamo.”