Police units in four key Bolivian cities declared themselves in mutiny against the government of president Evo Morales and joined protesters in demanding a second round of voting amid allegations of election fraud.

Officers from an anti-riot police unit unfurled a banner reading “Evo Morales Out!” from the roof of their station in Cochabamba, in the centre of the country.

Other police units used the opportunity to call for wage parity with the military and independence from political interference.

In response the government accused opposition political leaders of mounting a "coup" against the president.

"Sisters and brothers, our democracy is at risk due to the coup d'etat that violent groups have launched that undermine the constitutional order," Mr Morales tweeted in the early hours of Saturday. "We denounce this attempt against the rule of law before the international community."