UN Secretary General Ban Ki moon arrived in Burundi Monday to step up efforts to end months of political violence in the east African nation.
Ban was due to meet with Burundian Foreign Minister Alain Aime Nyamitwe on Monday afternoon and President Pierre Nkurunziza on Tuesday.
Nkurunziza has insisted he will not meet exiled opposition politicians, whom his government accuses of being behind a failed coup in May last year.
Leonard Nyangoma, the chairperson of the CNARED organization for government opponents in exile, said Ban's visit is an opportunity to pressure Nkurunziza into negotiating with his foes.
"Going forward, Nkurunziza has no choice. He has to negotiate,” Nyangoma said.
Ban should also press Nkurunziza into allowing independent experts to investigate human rights abuses in the country.
Burundi has been gripped by political violence since Nkurunziza announced in April that he would seek a third term in office, and won an election in July.
Hundreds of people have been killed in protests, clashes and assassinations, while a newly formed rebel movement has vowed to oust him from power by the use of force.
Opponents and supporters of Nkurunziza have targeted each other in gun, rocket and grenade attacks. The violence has spread to the provinces.
Hours before Ban arrived, one person was killed and another was wounded in a grenade attack at a Bujumbura market.
The European Union, the African Union and the United Nations have all sought to broker a peaceful solution to the crisis.
In December, the EU held consultations with the government of Burundi, after accusing it of failing to comply with the principles of human rights, democracy and the rule of law agreed to under a treaty signed in 2000 by European, African, Caribbean and Pacific states.
A decade ago, around 300,000 people were killed in a civil war in Burundi fought between the Hutu and Tutsi ethnic groups.