Government officials said the charges were illegal, but civic leaders in Santa Cruz argued that sending in the army was out of proportion with the problem.

"An act of corruption does not justify sending the army," Branco Marinkovic, the leader of a group created in the 1950s to push for greater regional autonomy, told the Reuters news agency.

Tear gas fired

Riot police dispersed protesters with tear gas when they tried to storm the airport on Thursday, but after Ruben Costas, governor of Santa Cruz, on Friday called for citizens to retake the airport the troops moved away.

Costas said that the soldiers had left "with their tails between their legs".

Protesters demanded greater autonomy and 
objected to government policies [Reuters]
"They should learn to resort to justice," instead of using the military to solve their problems, he told marchers gathered at the airport.

Morales said in a televised address that he had ordered the security forces to withdraw to prevent violence.

At least two soldiers had been wounded in Thursday's operation and local hospitals reported that another 20 people were injured.

Juan Ramon Quintana, a senior aide to Morales, called the seizure "a defeat for the people of Bolivia".

Santa Cruz is the centre of Bolivia's energy industry and its leaders want autonomy from the capital La Paz and a larger share of their state's natural gas revenues.

Morales, a close ally of Hugo Chavez, Venezuela's president, and Fidel Castro, his Cuban counterpart, has said part of the money from the nationalised industries will be used to fuel "indigenous socialism".