Victims of the 50-year-old armed conflict in Colombia called on President Juan Manuel Santos Thursday to protect witnesses testifying in peace talks and investigate death threats against them.

The U.S. Secret Service director resigned Wednesday, paying the price for a string of security lapses by the elite presidential protection branch, including one in which an armed intruder ran into the White House.

A third Colombian pleaded guilty Wednesday to participating in the kidnap and murder of a U.S. Drug Enforcement Administration agent in Bogota last year, the U.S. Justice Department said.

Hector Leonardo Lopez, 34, was part of a gang  who targeted DEA agent James Watson for a so-called "millionaire's ride" in June 2013.

Colombia's leftist FARC guerrillas denied government accusations Tuesday of collaborating with drug traffickers to carry out a recent attack that killed seven police officers.

The rebel group's second-in-command, Ivan Marquez, said as he arrived for a new round of peace talks with the government that the accusations were "lies" and a distraction from the nearly two-year-old negotiations.

At least seven police officers were killed and seven wounded when gunmen from the FARC rebel group ambushed their convoy Tuesday in remote northwestern Colombia, officials said.

"This is a cowardly attack that deserves condemnation by all Colombians," President Juan Manuel Santos said during a speech in which he attributed the violence to the FARC and Colombia's "Clan Usuga" criminal gang.

Six guerrilla fighters with the Revolutionary Armed Forces of Colombia (FARC) were killed in an operation launched jointly by police and the military, officials said Friday.

The men died Thursday when government forces bombarded their rural encampment in the central state of Meta.

A Colombian man is being investigated for posing as a Lebanese diplomat after giving lectures on the Middle East and advising the Colombian military under a false identity, local media reported.

Jeyson Puello, a resident of the northeast city of Valledupar, was using diplomatic papers with a U.N. seal to pass himself off as Jason Ali Hakim Abdullaziz Al Nayb, supposedly a high-ranking diplomat and former Lebanese foreign minister, news reports said.

Colombian authorities said there was little chance of finding survivors after a small plane with 10 people on board crashed in the Amazon jungle.

A Colombian taxi driver pleaded guilty on Wednesday to his part in the kidnap and murder of a U.S. Drug Enforcement Administration (DEA) agent in Bogota last year, the U.S. Justice Department said.

Julio Estiven Gracia Ramirez, 31, was part of a gang of men who targeted DEA agent James Watson for a so-called "millionaire's ride" in June last year.

Leftist FARC guerrillas in peace talks aimed at ending a five-decade conflict rejected Monday a Colombian plan to put the military in charge of disarming the rebels.

"There is no way" that the Revolutionary Armed Forces of Colombia will accept a military role "to resolve issues that are of political nature by definition," top rebel negotiator Ivan Marquez told reporters.