CARACAS—Venezuelan prosecutors on Monday said they had charged opposition politician Freddy Guevara with terrorism and treason, among other allegations, after the country’s intelligence service arrested him from his car on a Caracas highway. Guevara is a close ally of opposition leader Juan Guaido, who is recognized as the South American country’s legitimate president by the United States and others. Guaido said unidentified armed men threatened him with arrest earlier on Monday as he left his apartment in an effort to assist Guevara. In a statement, the chief prosecutor’s office said it had sought an arrest warrant for Guevara due to his alleged “ties with extremist groups and paramilitaries associated with the Colombian government.” The incidents took place as the government and opposition prepare for negotiations planned for next month in Mexico with mediation by Norway aimed at resolving the South American country’s deep political crisis, people familiar with the matter …