Monitoring body the OSCE Monday gave Bulgaria's elections an overall clean bill of health but said that incidents during the campaign had undermined trust in democratic institutions in the ex-communist country.
The vote on Sunday was "held in a competitive environment, fundamental freedoms were respected, and the administration ... was well managed," the Organisation for Security and Cooperation in Europe said.
It added, however, that the campaign "was overshadowed by a number of incidents that diminished trust in state institutions and the process was negatively affected by pervasive allegations of vote-buying."
"When you look at the mistrust that exists between political parties, and at the current economic difficulties, this is a negative development," said Eoghan Murphy, who headed head the body's biggest mission to Bulgaria since 1990.
On Saturday opposition politicians reacted with uproar after authorities discovered 350,000 unaccounted-for ballot papers at a printing firm whose owner is reportedly close to ex-premier Boyko Borisov's GERB party.
Socialist party leader Sergey Stanishev said the discovery was "preparation for the total falsification of the elections," calling it a "scandal unseen in Bulgaria so far."
Five opposition parties -- excluding GERB -- also commissioned an independent vote count by an Austrian agency, although its findings broadly chimed with the official results.
Three months after mass protests forced his government's resignation, Borisov's GERB came first in the election, but well short of a majority and analysts predict he will fail to form a coalition.