Several of Bolivia's nine regions want more autonomy

Santa Cruz, Beni and Pando - Bolivia's richest regions - are angry at the reforms that include greater state control of the economy.

Another region, Tarija, is expected to follow suit.

Security forces are on alert ahead of rallies in the four provinces. Mr Morales said the moves were "illegal".

The regional protests coincide with a rally in La Paz, the president's stronghold, where members of the Constitutional Assembly are due to deliver the new constitution to Mr Morales.

The constitutional reforms will be then put to a referendum later this year.

Deep splits

The provinces of Beni and Pando declared autonomy at the rallies after the wealthiest region, Santa Cruz, backed a statute on Thursday under which it would keep two-thirds of its tax revenues.

President Morales' mostly supporters are gathering in La Paz

The autonomy charters will now be put to the local populations for approval.

Some 400 extra police have been sent to Santa Cruz, and the army has been told to prepare to protect public buildings.

The moves towards autonomy come after an assembly dominated by supporters of President Evo Morales adopted the new national charter article by article last weekend.

Mr Morales 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.

Indigenous rights

Low-lying Santa Cruz is the most prosperous part of South America's poorest country, having major agricultural businesses and much of Bolivia's oil and gas wealth.

Pro-autonomy supporters object to the new constitution, which would allow consecutive five-year presidential terms, increase indigenous rights and redistribute wealth to the poorer highland areas of Bolivia.

On Thursday, Mr Morales called for dialogue, but warned that the unity of Bolivia was inviolable.

"The unity of the country is untouchable, it is not up for discussion. There is no referendum to be held on the country's unity," Mr Morales said.

There were frequent demonstrations - both for and against - during the debate over constitutional reforms, with protests sometimes turning violent.