Supporters of Bolivian President Evo Morales protest in La Paz on Sept. 12. (Juan Karita/Associated Press)

The "massacre" of peasants in the rebellious province of Pando justified the imposition of martial law, Bolivian President Evo Morales said Saturday.

At least 16 people were killed in fighting in Pando Thursday, and two more died Friday at a provincial airfield when government soldiers opened fire on anti-government protesters.

Most of the 16 killed Thursday were peasant supporters of Morales. "These people were massacred," the president told reporters on Saturday.

Separatists in Pando and three other provinces in eastern Bolivia have occupied government offices, airfields and natural gas facilities to protest the government's plans for a Dec. 7 referendum on a new constitution, which would give Morales more power and transfer property to landless peasants.

Morales, the country's first indigenous president, is trying to improve the lot of the poor indigenous population, but has run into opposition in the richer eastern provinces.

Morales said he would extend the martial law order to the other three provinces, if necessary.

Emergency meeting on Monday

The violence led Chilean President Michelle Bachelet to call for an emergency meeting of South American leaders on Monday.

"A larger tragedy has to be avoided," Venezuelan President Hugo Chavez said.

"We all agree that we have to look for a point of compromise," said Carlos Dabdoub, a key official in Santa Cruz, Bolivia's richest province and one of the rebellious provinces.

Morales and Chavez both expelled the U.S. ambassadors from their countries last week, alleging the U.S. is backing the anti-government protesters in Bolivia.

U.S. officials have denied the claim.