Voting overshadowed
 
Lucia Newman, Al Jazeera's correspondent in Santa Cruz, said government supporters blocked roads to prevent people from reaching polling stations.
 
"They have burned ballot boxes and in some areas there have been various serious clashes between pro and anti-government groups," she said.
 
"The turnout has been pretty high but these kinds of violent incidents are marring the process."
 
The move towards self-rule in Santa Cruz, which holds important gas resources, is expected to gain significant backing.
 
Surveys have suggested that up to 70 per cent of the region's 900,000 voters could support the move.
 
Local authorities in the eastern region are expected to pass laws giving them greater power over the province's finances and security operations if the referendum is passed.
 
'Serious consequences'
 
Newman said that the Santa Cruz vote was just the beginning of a series of ballots on autonomy in Bolivian regions.
 
"After this vote, there will be three other provinces that will follow suit. There is going to be a domino effect - a large part of Bolivia is going to be voting for autonomy," she said, speaking in Santa Cruz.
 
"While [the vote] may technically not be constitutional, there is a certain political legitimacy because it comes from a democratic vote.
 
Surveys suggest that 70 per cent of Santa Cruz
voters will support greater autonomy [EPA]
"This is going to force the government to negotiate. Both sides need each other and, despite what the government is saying, neither the state nor the provinces want to break away. There is an impasse here."

Mario Ayala Ferrufino, permanent secretary of the Supreme National Defence Council, said on Saturday that the vote was a threat to the territorial integrity of Bolivia.
 
The vote could raise "serious consequences for the unity of the country that are in total contradiction" with the constitution, he told the Erbol news agency.

The situation has exposed the divide between the indigenous Indians, who make up 60 per cent of the population and largely live in the Andean mountains, and the better-off inhabitants of the lowlands, many of whom have European ancestors.

About 5,000 indigenous Indians held a rally in the city of Santa Cruz on Friday in protest at the referendum.

Fidel Surco, the leader of a powerful indigenous rural group, told the crowd at the rally that if violence broke out "the responsibility for a bloodbath" would rest with Santa Cruz's authorities for organising the referendum.

Morales, the country's first indigenous president, has not followed through with a threat to bring troops into the region, but violence between his supporters and those backing autonomy is feared.

'Unconstitutional' poll

Morales has said that he will ignore the result of the vote, calling the move unconstitutional and separatist.
 
"They're only in it for the money, not for the country. They're only in it to help out a few businessmen, and not the people," he told the Associated Press news agency on Saturday.

Leaders in Santa Cruz want greater autonomy in order to keep more of the province's natural gas revenues and to protect their large plantations and ranches from Morales' plan for land redistribution.

Morales has said that he needs a strong central government to distribute Santa Cruz's wealth to the rest of the country.

On Friday, Morales suggested that the dispute could be decided by a nationwide referendum.
 
However, he also said that some of the state's demands may be worked into Bolivia's new constitution if the referendum is approved.

"If we politicians can't find a way to agree, let the people decide with their vote," he said.

Three others provinces are to hold their own votes on autonomy next month, while two more are considering holding a referendum.