The United Nations has called on political parties in Burundi to commit fully to peace talks to resolve a two-year old political crisis in the east African nation.

Burundi President Pierre Nkurunziza's government said earlier this month it would not attend the talks led by the East African Community (EAC) aimed at ending the crisis sparked by his decision to run for a third term in office.

"I urge all Burundian stakeholders to place their country's interests above their own and to commit in good faith and without preconditions to a truly inclusive and credible EAC-led dialogue," U.N. Secretary General Antonio Guterres said in a report to the U.N. Security Council.

The government, which has repeatedly accused the U.N. of bias, said it objected to the presence of senior U.N. adviser Benomar Jamal at the talks, which are being held in neighbouring Tanzania.

The main opposition grouping CNARED said it would attend the talks, which are being mediated by Benjamin Mkapa, a former president of Tanzania.

In the report, Guterres said the U.N. would keep supporting the efforts to peacefully resolve the impasse, in order to secure stability in the region.

"The fact that the crisis in Burundi has not escalated into a full-blown armed conflict so far is not an indicator that the worst has been averted," he said.