Colombia's most prominent labor leader charges its army with targeting unionists for death: The men were killed on Thursday by troops sent to arrest them near the eastern town of Saravena, one of the most violent places in Colombia and where Marxist rebels enjoy popular support. Vice President Francisco Santos said the three belonged to the outlawed National Liberation Army, a 5,000-strong force with a strong presence in the oil-rich region near the border with Venezuela. "They were union officials. But they were also mixed up in things which didn't have anything to do with their union work," Santos told reporters on Friday. General Luis Fabio Garcia said the men were carrying weapons and explosives when they were shot. But the president of Colombia's largest labour organisation, the Central Workers' Union, said the officials died just one day after they said there was a plot to murder them. "We consider this to be an assassination of union officials," Carlos Rodriguez told Reuters. The office in Colombia for the U.N. High Commissioner for Human Rights called for an investigation, as did representatives of Amnesty International, who met President Alvaro Uribe on Thursday to ask for guarantees for the security of rights workers.