Bujumbura - Burundi's foreign minister on Thursday denied reports that mass graves containing the bodies of government opponents existed in and near the capital Bujumbura.
"It is a campaign of mudslinging against the authorities in Bujumbura," Alain Aime Nyamitwe told journalists.
"Let us wait for the results of an investigating commission which has been ordered by the attorney-general," he added.
Nyamitwe was reacting to a statement by Amnesty International last week that satellite images, video footage and witness accounts indicated the existence of mass graves containing dozens of bodies.
"These images suggest a deliberate effort by the authorities to cover up the extent of the killings by their security forces and to prevent the full truth from coming out," said Muthoni Wanyeki, a director of the human rights group for east Africa.
"After the investigations, the Burundian government will be prepared to work with Amnesty International to discover the truth on these mass graves," Nyamitwe said.
Burundi has been gripped by violence since President Pierre Nkurunziza announced in April that he would seek a third term, despite the constitution setting a two-term limit.
More than 400 people have been killed in protests, clashes and attacks by police and government opponents, according to the UN and human rights activists.
CNARED, an organization for government opponents in exile, meanwhile warned that Burundi was in danger of sliding into a new civil war. The 1993-2005 civil war, which pitted the majority Hutus against the minority Tutsis, left 300 000 people dead.
Nyamitwe denied reports that police targeted especially Tutsis when arresting government opponents. "These allegations have no foundation," he said. "Everybody knows that the Burundian conflict is not ethnic, but rather political."
Many of the opposition leaders are Hutus, Nyamitwe pointed out.