Belarussian President Alexander Lukashenko has warned he will not tolerate any attempt at a "coup" as he runs for a third term on Sunday.
Officials in the ex-Soviet republic have accused foreign countries of backing opposition candidates in the presidential election.
The US and EU accuse Mr Lukashenko of authoritarian methods.
Nine Georgian MPs and two Polish reporters were the latest foreign observers to be denied entry.
The head of Belarus' security service, Stepan Sukhorenko, has said the opposition plans to use Sunday's election to seize power by force.
One opposition candidate, Alexander Milinkevich, denied the accusations and said the election would be rigged.
Opinion polls are virtually non-existent in Belarus and exit polls are not due to be taken.
'No conflicts here'
In a final televised election address on Friday, President Lukashenko warned foreign monitors not to "exceed their remit".
"Observe, draw conclusions, but do not decide for us... what path the Belarusian people should take," he said.
Mr Lukashenko defended his record in office, saying the economy was strong and the republic had avoided "social, political, racial and religious conflicts".
Arguing that the presence of four rival candidates was proof of democracy, he warned that political violence would not be tolerated.
"I guarantee that there won't be a coup d'etat in this country," he said.
Large-scale street protests led to the fall of leaders in other ex-Soviet republics, notably Ukraine and Georgia.
Alexander Kozulin, one of the opposition candidates, told a rally in Minsk on Friday that nobody wanted "violence" but he called for a mass demonstration.
"I appeal to all voting against Lukashenko to go into the street and thus prove that the results are rigged," he told the rally of about 1,000 people.
"It is time for Belarus to awaken and shake off its fascist dictatorship."
Belarussian Foreign Minister Sergei Martynov told EU ambassadors on Thursday that responsibility for the consequences of any mass disorder would lie with the opposition and foreign governments which backed it.
European Union foreign policy envoy Javier Solana expressed "indignation and surprise" at the warning.
Any crackdown on opposition rallies would, he said, "meet with a strong international reaction".
"We are deeply concerned about those reports. We're deeply concerned about the direction of the government of Belarus and their lack of moving in a democratic direction,"
The White House has also expressed "deep concern" about reports of a crackdown.
"This is one country... that has moved in the opposite direction of democracy and freedom," said spokesman Scott McClellan.