The United States accused the country's authorities of trying to undermine democratic institutions.
A U.S. statement to the Organization for Security and Co-operation in Europe (OSCE), said that in recent weeks, authorities in Minsk have harassed and intimidated non-governmental organizations, opposition political figures, and civil society groups.
The U.S. spokesman, Bruce Connuck, listed a number of groups that he said had suffered harassment.
Connuck told the OSCE in Vienna that there is a "growing atmosphere of intimidation" against these targets.
The U.S. diplomat also accused the Belarus authorities of manufacturing conspiracies and crises to justify its repression.
The EU Adds Its Voice
Also today, European Union External Relations Commissioner Benita Ferrero-Waldner condemned what she called "serious violations" of the campaigning rights of the opposition candidates.
Her statement says the EU is particularly concerned by reports of the detention of Alyaksandr Kazulin, one of the four registered candidates in the race. Kazulin was held for several hours today and allegedly beaten before being released.
She also noted that a declaration adopted by EU foreign ministers in January said the EU is ready to take "further appropriate restrictive measures against the responsible individuals" if the elections are not conducted in a democratic manner.
President Lukashenka's warning came during a speech in Minsk as thousands of opposition supporters rallied in the streets of the capital against his regime.
Lukashenka said tension was rising in Belarus ahead of the vote and urged vigilance against "provocations."
(with additional agency material)