Burundi's parliamentary elections on Monday were not fair or free and human rights were violated, the United Nations said on Thursday.
In Washington, the State Department said the United States suspended several security assistance programs it had with Burundi.
Burundi has been locked in its worst political crisis since its civil war ended a decade ago, with protests erupting in late April against President Pierre Nkurunziza's bid to seek a third term in office. Dozens have been killed.
The opposition boycotted the parliamentary election on Monday. A presidential vote is scheduled for July 15 and the UN and others have called for it to be postponed. Opponents say the president's attempt to stand again violates the constitution.
U.N. spokesman Farhan Haq said the preliminary conclusion of the U.N. electoral observer mission in Burundi was that "the overall environment was not conducive for free, credible and inclusive elections."
"Episodes of violence and explosions preceded and in some cases accompanied election day activities," Haq said. "The U.N. mission ... observed media freedom restrictions, violations of human rights and fundamental freedoms."
"This includes infringements to the right of the political opposition to campaign freely, extra-judicial killings, arbitrary detentions, and acts of violence committed by armed youth groups aligned with political parties," he said.
U.S. State Department spokesman John Kirby said the United States urged Nkurunziza "to place the welfare of Burundi's citizens above his own political ambitions and participate in dialogue with the opposition and civil society to identify a peaceful solution to this deepening crisis."
Kirby said this should include the delay of the July 15 presidential elections until conditions are in place for free, fair and peaceful elections.
"In response to the abuses committed by members of the police during political protests, we are suspending all International Law Enforcement Academy and Anti-Terrorism Assistance training that we provide to Burundian law enforcement agencies," Kirby said in a statement.
At least six people, including one policeman, were killed in Burundi's capital on Wednesday, witnesses and a police spokesman said.
About 140,000 people have fled the country, stoking concern in a region with a history of ethnic conflict, particularly in Rwanda, where 800,000 people were killed in 1994.
New Zealand's U.N. Ambassador Gerard van Bohemen, president of the U.N. Security Council for July, said the 15-member body expressed concern "that the minimum conditions for free, fair, transparent and credible elections were not met."
