Clashes have broken out in Bolivia as President Evo Morales appeared set to win re-election in controversial circumstances.
Counting was halted on Sunday as it looked as if the vote was heading towards a second round run-off.
But when it resumed President Morales had the narrowest of leads. His rival Carlos Mesa says he will not recognise the result.
One set of observers called the change “drastic and hard to explain”.
“We hope that the result of the final calculation will adhere to the will of the voters expressed at the poll,” the Electoral Observation Mission of the Organisation of American States (OAS).
It said in a statement that there was a “drastic and hard to explain change” in the results.
On Monday, protesters set fire to electoral offices in regions of Sucre and Tarija, according to local media, while in the capital La Paz demonstrators scuffled with police.
On Sunday, the website showing the preliminary results stopped updating at 83.8% of the votes.
The count showed Mr Morales leading with 45.3%, leaving Mr Mesa in second place with 38.2%.
When the website was updated on Monday, Mr Morales had a lead of 46.85% of votes against Mr Mesa’s 36.74%. The 10-point lead means he avoids having to go to a second round in December.
As counting was suspended, Mr Morales told his supporters he was confident that when votes from rural areas were counted, there would be no need for a run off.