(CNN) -- Tensions were rising in Bolivia on Saturday as members of the country's four highest natural gas-producing regions declared autonomy from the central government.

Ruben Costas, center, governor of Santa Cruz, celebrates as the Bolivian region declares autonomy Saturday.

Thousands waved the Santa Cruz region's green-and-white flags in the streets as council members of the Santa Cruz, Tarija, Beni and Pando districts made the public announcement.

The officials displayed a green-bound document containing a set of statutes paving the way to a permanent separation from the Bolivian government.

Council representatives vowed to legitimize the so-called autonomy statutes through a referendum that would legally separate the natural-gas rich districts from President Evo Morales' government.

The move also aims to separate the states from Bolivia's new constitution, which calls for, among other things, a heavier taxation on the four regions to help finance more social programs.

"The statutes will be ratified," said Oscar Ortiz, Santa Cruz senator. "With a public referendum, the people of our region will legitimize their will."

About 35 percent of Bolivia's 9.5 million people live in the four states, according to The Associated Press.

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In the meantime, Bolivian network ATV showed what appeared to be armed, pro-government protesters creating blockades around the town of Yapacani, on the outskirts of Santa Cruz.

Some indigenous pro-Morales groups claim Bolivia's richer, white-ruled Eastern regions want to control the country's natural resources. Bolivia has South America's second-largest natural gas reserves, behind Venezuela. Most of it is produced in the Eastern regions. Watch Bolivian leader speak out »

In the capital city La Paz on Saturday, Morales addressed thousands of flag-waving supporters in the Plaza Murillo, defending the new constitution and lashing out against what he called the racist policies of Bolivia's elite.

"They must give back the money they took from us," he told a cheering crowd, which included members of the Quechua and Aymara tribes. "We will retroactively investigate all the big fortunes, and the corrupt are now trembling with fear."

Morales also cautioned those who he said want a "a division, a coup d'etat," the AP reported.

"We won't permit Bolivia to be divided," he warned.

Morales -- who belongs to the Aymara indigenous group -- nationalized the country's oil and natural gas reserves when he took power in 2006, creating what became known as the "gas wars."

Running on a platform of redistribution of wealth among Bolivia's poor, Morales has defied countries such as Brazil and the United States for the exploration of Bolivia's natural reserves.

He has also protested the country's racial divide.

"Bolivia is a nation among nations," he said Saturday, referring to the diversity of Indian nations whose traditions date back centuries.

"We are not a country of blue-eyed, green-eyed folks only. It's a plurinational country made of dark-skinned and white-skinned. This new constitution will unite us." E-mail to a friend

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