Jairo Castillo said he received a call and faxed letter from Colombia’s witness protection program on Monday cautioning that two gunmen posing as tourists had been dispatched to kill him.The letter, a copy of which was published online Saturday by Colombia’s leading newspaper, El Tiempo, says “intelligence” uncovered the plot and advised Castillo to boost his security.An official in the chief prosecutor’s office confirmed the authenticity of the April 22 letter. He spoke on condition of anonymity because he is not authorized to disclose the information.The threats probably come from jailed former congressmen and/or paramilitary leaders still at large, Castillo told The Associated Press in a phone interview from Canada.He has claimed that politicians benefited personally and at the ballot box from ties with paramilitary warlords.Castillo’s testimony was key in convicting at least two politicians from his home state of Sucre.”We’re going for the part that no one likes people to touch: the finances,” he said. “Because I am going to insist on that part, they try to threaten me.”Castillo, 40, says he has intimate knowledge of meetings between politicians and paramilitaries in which politicians asked for help obtaining ranches cheaply.Beginning in the mid-1990s, paramilitaries killed thousands and drove tens of thousands more from their land as they rid most of Colombia’s Caribbean coast of leftist rebels, who extorted and kidnapped ranchers.Mario Uribe, a former senator who is the president’s second cousin and close confidante, was among those politicians who sought paramilitary help in obtaining cheap land in Sucre, Castillo told the AP in April 2007. Uribe has denied the allegations and called Castillo a liar.Uribe was jailed this week on charges of criminal conspiracy for allegedly supporting paramilitaries. His lawyer, Jose del Carmen Ortega, on Saturday called any suggestion that he could be involved in a plot to kill Castillo “false and crazy.”