Thousands of anti-government demonstrators marching in support of Bolivia's former President Evo Morales have clashed with counterprotesters blocking their way, a stark sign of an escalating power struggle in the volatile Andean nation.

In his most brazen show of force yet against current President Luis Arce, Morales sent word to his followers to mobilize what he called a "March to Save Bolivia," a 190-kilometer (118 mile)-trek from the small village of Caracollo to the capital, La Paz, denouncing the government of his protege-turned-bitter rival.