Bolivians yesterday approved a new constitution granting more power to the country's indigenous majority and rolling back half a millennium of colonialism, discrimination and humiliation.

After a bruising struggle between supporters and opponents of the president, Evo Morales, the country voted to adopt the new constitution in a referendum.

The charter confirms Bolivia – the second poorest country in South America after Guyana – as a leader in the regional "pink tide" of leftwing governments that have ousted traditional elites and challenged US influence.

Yesterday, Morales, who wept for joy when the draft of the new constitution was agreed last October, told a crowd in front of the presidential palace that the vote signalled the start of a new era.

"Here begins the new Bolivia," he said. "Here we begin to reach true equality."

The president said the charter would "decolonise" Bolivia by championing indigenous values lost since the Spanish conquest.

It also includes clauses on land redistribution and sets aside seats in Congress for minority indigenous groups.

However, in Boliva's conservative eastern lowlands, a semi-tropical stronghold of European descendants, there was widespread opposition to the constitution, with critics saying it was a recipe for ruin, division and authoritarianism.

They argued that the focus on indigenous communitarism ignored the freewheeling capitalism that drives the eastern plains' huge cattle ranches and powerful soy industry.

There were bloody clashes between pro and anti-government supporters, including miners armed with dynamite and peasants with machetes, during the drafting of the charter.

Several people died, hundreds were injured and Bolivia was left dangerously polarised.

Yesterday, Moises Shiriqui, the cowboy-hatted mayor of the eastern provincial capital, Trinidad, said there was still fierce opposition to the new constitution.

"In five states, we're rejecting the constitution," he said. "In five states, we have another vision of the country."

An unofficial tally by the Bolivian television network ATB showed the constitution winning with 59% of the vote.

The quick count had a 3% margin of error, and was mirrored by two private exit polls. An official vote count will be announced on 4 February.

The constitution also gives Morales the opportunity to run for re-election and remain in power until 2014.

He is expected to go to the polls again in December in an election that will also elect a newly reorganised Congress with seats set aside for minority indigenous groups.

A provision granting autonomy for 36 indigenous "nations" and four opposition-controlled eastern states is at the heart of the constitution.

But both groups are given a vaguely defined "equal rank", which critics say will create rival claims to open land in Bolivia's fertile east, home to the large agribusiness interests and valuable gas reserves that drive much of the country's economy.

With an eye to redistributing land in the region, the constitution limits future holdings to either 5,000 or 10,000 hectares (12,000 or 24,000 acres).

Current landholders are exempt from the cap in a nod to the cattle and soy industries.

Morales, an Aymara Indian, has allied himself closely with the Venezuelan president, Hugo Chávez.

He expelled the US ambassador and drug enforcement administration agents after claiming they had conspired against his government last year. Washington denied the allegations.

Elected in 2005 on a promise to nationalise Bolivia's natural gas industry, Morales has increased the state's presence throughout the economy and expanded benefits for the poor.

In 2006, his reform project nearly failed when an assembly convened to rewrite the constitution broke apart along largely racial lines.

The following year, three college students were killed in anti-government riots, and 13 mostly indigenous Morales supporters died when protesters seized government buildings to block a vote on the proposed constitution in September.