Gunmen in Burundi killed a policeman and a civilian in a nighttime raid, a governor said Wednesday, the latest in a string of attacks in the troubled country.

Four others were wounded in the shooting at the office of the ruling party soon after nightfall on Tuesday in the Ndava district in the central Mwaro region.

An African Union human rights report called on Friday for an international police force and more military and rights observers to be sent to troubled Burundi.

The AU rights investigators said it was "necessary that, apart from strengthening AU human rights monitors and military observers, an international police mission is deployed."

United Nations investigators have begun work in Burundi examining allegations of widespread abuses in the troubled central African country, U.N. sources said Thursday.

Hundreds have been killed and a quarter of a million people have fled Burundi since President Pierre Nkurunziza's controversial decision in April 2015 to run for a third term, a vote he won in July as the opposition staged a boycotts.

Burundi's main opposition group said Wednesday it had not been invited to long-stalled peace talks aimed at solving a year-long crisis, demolishing hopes the meeting could help strike a deal.

Talks were expected to run from May 21-24 in the northern Tanzanian town of Arusha but key umbrella opposition group CNARED were not invited, the group's spokesman Pancrace Cimpaye said.

Rwanda has expelled over 1,500 Burundians in recent days, government officials said Monday, amid worsening relations between the neighbors.

However, Seraphine Mukantabana, Minister of Disaster Management and Refugee Affairs, said the expulsions were part of a regular crackdowns on those living illegally in the country and were not targeting Burundians specifically.

Gunmen in Burundi killed at least five people and wounded seven when they opened fire on a market late Monday, government officials said, the latest attack in the troubled country.

The attack by unidentified insurgents took place in Burundi's eastern Ruyigi region, close to the border with Tanzania, local government district head Aloys Ngenzirabona said Tuesday.

The European Union, Burundi's biggest aid donor, on Monday suspended all direct funding to the government for ignoring human rights and failing to stop a wave of deadly violence.

Burundi has been in turmoil since July when President Pierre Nkurunziza won a third term which the opposition said was illegal.

Police in Burundi have arrested one of the last opposition leaders not to have fled the troubled country, his family and supporters said Wednesday.

Hugo Haramategeko, 47, president of the small Nadebu party, the New Alliance for the Development of Burundi, was arrested as he took a shower at home in the capital Bujumbura in a dawn raid by police, a family member said. The police could not be immediately contacted for comment.

Five African heads of state met with Burundi's president in Bujumbura on Friday at the end of a two-day visit to push for talks to end the country's political crisis.

The delegation's visit came just days after a trip by U.N. chief Ban Ki-moon as international efforts to bring an end to 10 months of deadly turmoil are stepped up.

A delegation of five African heads of state arrived in Bujumbura on Thursday at the start of a two-day visit to push for talks to end Burundi's deep political crisis.

The visit comes just days after a trip by U.N. chief Ban Ki-moon to Burundi as part of growing international efforts to bring an end to 10 months of deadly turmoil in the central African country.