Ugandan President Yoweri Museveni has arrived in Burundi for crisis talks as President Pierre Nkurunziza is preparing to run for a controversial third consecutive term in office.

Museveni arrived in the Burundian capital Bujumbura on Tuesday to revive stalled talks between President Nkurunziza-led Forces for the Defense of Democracy (CNDD-FDD) party and opposition groups.

The veteran Ugandan leader was appointed as mediator by the five-nation East African Community (EAC) last week.

President Museveni has said in a statement that he would "establish a dialogue among warring political factions" in Burundi to solve the crisis.

The visit comes after Nkurunziza announced on Saturday the postponement of the country’s upcoming presidential elections from July 15 to July 21 apparently under international pressure.

Reacting to the visit, Presidential Nkurunziza's communication adviser Willy Nyamitwe said he hoped Museveni would convince the opposition to take part in the upcoming presidential polls next week.

Burundi opposition leader Leonce Ngendakumana has demanded that Museveni convince the president to step down.

"It is black and white," Ngendakumana said.

The opposition has boycotted the presidential polls, leaving only the ruling CNDD-FDD and its affiliated parties to compete for the presidency.

Nkurunziza's bid to stand for a third consecutive five-year term has sparked months of violence and an attempted coup in mid-May.

Opposition groups say another term would violate a constitutional two-term limit and a peace deal that paved the way to end a 12-year civil war in 2006.

The opposition also argues that weeks of violent crackdown on protesters by security forces means free and fair elections are impossible.

International community has also voiced concern that the ongoing crisis could plunge the impoverished, landlocked country back into civil war.

Nearly 80 people have been killed by government forces and over 158,000 Burundian refugees have fled to neighboring countries due to the violence.