With three weeks left until elections in Tanzania, East Africa's most populous nation, tensions are rising ahead of what is expected to be tightest electoral race in the country's history.

The front-runner in the presidential race appears to be John Magufuli, candidate for the long-ruling Chama Cha Mapinduzi (CCM), who is hoping to succeed President Jakaya Kikwete, who is stepping down after the constitutional two-term limit.

The defence team for Laurent Gbagbo, who is currently awaiting trial for war crimes in The Hague, on Friday asked that the ex-Ivorian leader be tried on his home continent instead.

Gbagbo's trial at the International Criminal Court (ICC) is due to open in November, with the former president accused of crimes against humanity after his refusal to concede defeat in 2010 elections sparked a bloody stand-off in which some 3,000 people died.

President Pierre Nkurunziza's bid to win a third term "seriously undermines Burundi's stability" and violates the Arusha Agreement that brought its 13-year civil war to an end, the U.S. said late Monday.

"Any violation of Arusha seriously undermines Burundi's stability," the statement issued by the U.S. embassy in Bujumbura said.

Some 3,000 cases of cholera have been reported in Tanzania, mainly among Burundian refugees fleeing political violence, the U.N. said Friday, adding that up to 400 new cases were being counted daily.

So far, 31 people have died of the water-borne disease in the area around the western Tanzanian border town Kaguna, which has been flooded with refugees, the U.N. refugee agency said.

The United States on Sunday helped evacuate American, Canadian and other foreign citizens from Burundi, rocked by weeks of deadly street protests and an attempted coup, a State Department spokesman said. 

Burundi's streets have been mired in violence since the announcement by President Pierre Nkurunziza that he would stand for a third term in office. 

Burundi's President Pierre Nkurunziza on Sunday made his first appearance since an attempted coup, looking relaxed and sending a clear message he was back in charge of the central African nation.

Dressed in a blue blazer and polo shirt, the president smiled and shook hands with reporters at the presidency in Bujumbura's city center. He gave only a brief statement, without even mentioning this week's attempt to overthrow him.

The United Nations has sent reinforcements to its Democratic Republic of Congo peacekeeping force near the eastern town of Beni, after two soldiers were killed and 13 others wounded in an ambush Tuesday. 

"This morning we sent reinforcements to the Beni area -- a rapid response unit to back up those caught in ambush," Felix Prosper Basse, spokesman for the U.N.'s MONUSCO DRCongo mission, told AFP a day after two Tanzanian peacekeepers and two civilians were killed near Beni.

The leader of a Ugandan rebel group with alleged links to al-Qaida has been arrested in Tanzania, state-owned Ugandan media reported Thursday.

Uganda's New Vision newspaper said Jamil Mukulu, leader of the Allied Democratic Forces (ADF), was being held in Tanzania ahead of his extradition.

At least 19 Tanzanian gold miners were killed when the pit they were working in collapsed in the northwestern Msalala district, a local government official said Saturday.

"The pit collapsed and buried several people who were working in it, efforts are going on to dig out more bodies," said local district commissioner Benson Mwampesaya, saying 19 bodies had been recovered.

Malawi has ordered police to shoot "dangerous criminals" who attack albinos in order to sell their body parts for witchcraft.

"Shoot every criminal who is violent when caught red-handed abducting people with albinism," the country's police chief Lexen Kachama told officers at the weekend, according to local media.