Johannesburg - Reports of mutilated corpses are again emerging as Burundi's political crisis continues, a United Nations expert on the East African nation says.Such corpses were seen in 2015 and early 2016 but reports have resumed in recent months, the president of the UN commission of inquiry on Burundi, Fatsah Ouguergouz, told the UN Human Rights Council on Monday. In many cases neither victims nor suspected perpetrators could be identified.Burundi has been in turmoil since President Pierre Nkurunziza in 2015 successfully pursued a third term that many called unconstitutional.Hundreds have died and nearly 500 000 people have fled the country.Attempts at peace talks between the government and opposition have failed.The UN secretary-general has warned that if Nkurunziza pursues a fourth term it could cause "an even deeper crisis." The president has mentioned the possibility if Burundi's people decide to change the constitution.Allegations of torture and forced disappearances continue in Burundi, the UN expert said on Monday. Journalists who fled the country at the height of tensions in 2015 have not found it safe to return."The quasi-total impunity for the perpetrators of these violations particularly troubles us," Ouguergouz told the Human Rights Council.Burundi government officials have disputed reports of abuses.