"Sisters and brothers, our democracy is at risk due to the coup d'etat that violent groups have launched to undermine the constitutional order", he wrote on Twitter late on Friday.
In the city of Cochabamba, the scene of recent violent clashes, Reuters witnesses saw police officers protesting on the roof of their headquarters in an apparent act of disobedience against the government.
For his part, Defense Minister Javier Zavaleta denied in a press conference that the Armed Forces had taken to the streets following the mutiny of police officers in Cochabamba.
On Friday night crowds cheered dozens of police officers who marched down a main avenue and garrisoned themselves in the city's central police station.More news: Kourtney Kardashian confirms she's stepping away from 'KUWTK'
The dispute over the presidential election has triggered nationwide protests, resulting in three deaths and more than 300 injuries.
Camacho plans to lead a march to the government palace on Monday with a pre-written symbolic resignation letter for Morales to sign.
Local news reports on Saturday indicated groups of police in the cities of Tarija, Oruro and Beni, had also joined their colleagues in Santa Cruz, Sucre and Cochabamba in rebelling against Morales' government.
A former president himself, he asked Bolivia's congress on Friday to pass an emergency bill to prepare for new elections.More news: Swedish climate activist Greta Thunberg getting mural in San Francisco
In some La Paz neighborhoods, police retreated to their barracks rather than take on protesters who shouted: "Police, our friends, the people are with you".
In his toughest ever electoral race, Morales claimed victory with just enough votes to avoid a second-round runoff.
However, his call for dialogue was promptly rejected by several political parties and his closest rival in last month's election, Carlos Mesa - who as a candidate would not have been invited to participate.
In addition, tension increased Thursday in the capital with the arrival of the president of the Pro Santa Cruz Committee Luis Fernando Camacho to whom Vice President Alvaro Garcia Linera accused of being one of those responsible for the violence generated in the country and to promote a coup d'etat. But a 24-hour lapse in releasing vote results raised suspicions among opposition supporters.More news: Nunes demands Schiff testify in private as part of House impeachment inquiry
The Organization of American States is conducting an audit of the election count and their findings are expected next week. The opposition says it will not accept the results because they were not consulted on how the process would unfold. The country's constitutional court later ruled that term limits violated his human right to run for office, and the electoral court ultimately accepted his candidacy for a fourth term.