Venezuelan riot police fired tear gas at a demonstration in Caracas called by opposition leader Juan Guaido on Tuesday to demand presidential elections. Thousands of protesters started marching from the east of Caracas towards the National Assembly legislature when they were blocked by a police barricade. As Guaido spoke to the demonstrators proposing an alternative route, police fired tear gas at them, AFP reporters at the scene said. gm/at/lda/bc/ft