United Nations - UN Security Council envoys will press Burundi's government to agree to talks with the opposition under a new mediator when they travel to Bujumbura this week, a UN envoy said on Monday.Diplomat Jamal Benomar said the dialogue must be impartially-mediated and have a clear timeline after Uganda's failed bid to broker a deal to end months of violence in Burundi.On Thursday, the 15 council ambassadors will be making their second trip to Burundi in less than a year, hoping to avert what some fear could be a return to all-out war."There is a window for the Burundians to come together and work out a way on how they can move forward," Benomar told reporters."For them to do this, they would need an inclusive process that is impartially-mediated. "One that has a timeline that is clear, an agenda, an agreement on who will participate, and this is exactly what we don't have."The envoy did not say that the UN should take on that role, but the world body is beefing up its presence in the country with the dispatch of a 20-member team this week.Alarms flashing redBurundi descended into bloodshed in April when President Pierre Nkurunziza announced his intention to run for a controversial third term, which he went on to win in July.Hundreds of people have died in the violence and some 70 000 have fled to neighboring countries.UN human rights chief Zeid Ra'ad al-Hussein last week said "all the alarm signals, including the increasing ethnic dimension of the crisis, are flashing red." He called for an urgent rights investigation.Zeid cited allegations that Burundi's security forces had gang-raped women, dumped bodies in mass graves and were increasingly resorting to torture.Describing the conflict in Burundi as complex, Benomar said rights violations were taking place "in the context of an insurgency and counter-insurgency."Council envoys are to arrive in Bujumbura on Thursday for two days of meetings with the opposition, civil society and with Nkurunziza.The diplomats are also planning a stopover in Addis Ababa for talks with the African Union on its proposal to send a peacekeeping force to Burundi after the government rejected the offer.