The autonomy referendum for Bolivia's richest province of Santa Cruz on Sunday was "illegal and unconstitutional," President Evo Morales said in a national broadcast after the poll.
"This illegal and unconstitutional vote didn't have the success hoped for by certain families," he said.
Morales also called for dialog with opposition governors seeking greater political and economic autonomy from the government.
The referendum began at 8 a.m. local time (1300 GMT) Sunday and led to confrontations that left at least one person dead and 30 injured.
According to preliminary results, over 85 percent of Santa Cruz inhabitants voted in favor of autonomy for the province, but Morales said that as many as half the ballots were invalid.
International and regional organizations such as the United Nations, the Organization of American States and many Latin American governments are opposed to the autonomy referendum.
They fear the referendum would plunge Bolivia into chaos and urged dialogue between the two sides.
(Xinhua News Agency May 5, 2008)