KAMPALA, Uganda -- An outbreak of cholera has infected 3,000 people in a Tanzanian border region where refugees fleeing political unrest in Burundi have massed, the U.N. Refugee Agency said Friday.

Some 300 to 400 new cases of cholera are being reported daily. At least 31 people -- 29 refugees and two Tanzanians -- already have died of the disease, according to UNHCR.

More than 64,000 Burundians have fled to Tanzania in recent weeks, UNHCR said, escaping the unrest sparked by their president's bid for a third term that many say is unconstitutional.

UNHCR and its partners appealed for help Friday, saying $207 million is needed to respond to the humanitarian crisis and assist some 200,000 Burundians who have taken refuge in Tanzania, Congo and Rwanda.

The refugee agency said the number of people fleeing Burundi could double in the next six months.

Between 500 and 2,000 Burundians are arriving daily in Kagunga -- many more than the population of the tiny fishing village on the shores of Lake Tanganyika.

The World Health Organization has warned that a "severe humanitarian crisis" is unfolding in Tanzania with refugees overwhelming health and sanitation facilities in the border area.

Cholera is a fast-developing, highly contagious disease that causes diarrhea, leading to severe dehydration and possible death. It is caused by contaminated food and water. Cases of acute diarrhea have also been confirmed among the refugees, who include many women and children.

Demonstrators in Bujumbura, Burundi's capital, say they will continue to protest until President Pierre Nkurunziza steps down at the end of his second term. Police have been using live ammunition and tear gas to disperse crowds of angry protesters, and observers have urged the government not to launch revenge attacks in the aftermath of a failed attempt by some military officers to force Nkurunziza out.

U.N. Secretary-General Ban Ki-moon is encouraged by U.N.-guided political talks in Burundi among representatives of the government, political parties and others, but he has expressed concern about the refugees and urged the Burundi government to "create conditions for their return," his spokesman's office said in a statement.