Opposition leaders in six of Bolivia's nine provinces have called a general strike for Wednesday in protest at a new draft constitution.
Feelings are running high over the proposed changes
At least four people died in the city of Sucre over the weekend after violent protests broke out against the reforms.
President Evo Morales says the new charter is part of a democratic revolution but opponents say the proposed reforms concentrate power.
The UN and the US are among those calling for calm.
In New York, UN Secretary General Ban Ki-moon urged all sides to refrain from violence.
President Morales says constitutional changes are key
"In order to strengthen democracy and respect for human rights in Bolivia, the secretary general urges all political and social actors to remain calm, to abstain from using violence and to seek a consensus on the pressing issues affecting the Bolivian people," a statement from his office said.
The US state department called on President Morales and the opposition "to show restraint and tolerance".
In Sucre, people have begun clearing up after three days of unrest left at least four people dead and hundreds injured.
Residents' groups were patrolling the streets after police fled their posts.
The protests erupted after a special assembly meeting at an army-run high school on the outskirts of Sucre approved the broad outlines of the draft constitution.
In the absence of opposition delegates, who boycotted the session, the assembly voted by a simple majority to approve all of President Morales's draft proposals.
The final draft will be put to a national referendum but no date has yet been set.
The president has made rewriting the constitution a key part of his reform agenda to give the indigenous majority greater political power but the issue has deepened regional and ethnic divisions in the country.
There is disagreement about which city should be Bolivia's capital
On Monday, Mr Morales led a rally in La Paz in support of the proposed changes.
At the same time, people seeking more autonomy from the central government organised a counter-demonstration in the capital of the gas-rich province of Santa Cruz.
One of the key sticking points has been the designation of the country's capital.
Sucre has seen weeks of unrest, with protesters taking to the streets in support of an opposition proposal to make the city the sole capital of Bolivia.
It is currently home to the Supreme Court, and was Bolivia's capital until 1899, but since then it has shared the title with La Paz.