Southern Sudan is facing a "serious outbreak" of the deadly kala azar tropical disease, the aid agency Medecins Sans Frontieres (Doctors Without Borders) warned on Friday.

Outbreaks have been recorded in several locations across the remote states of Jonglei and Upper Nile, with more than 380 patients being treated since October.

That is more than three times the rate recorded for the whole of the previous year, when only 110 cases were treated, MSF warned.

- We suspect that the number of kala azar patients reaching clinics in some areas is just the tip of the iceberg - said Dr David Kidinda, MSF medical coordinator for southern Sudan.

- Without treatment, those infected with kala azar can die within weeks if their immune system is already weakened - Kidinda added.

Almost all untreated victims die within one to four months

Kala azar, or visceral leishmaniasis, is a neglected tropical disease contracted by the bite of a sand fly, endemic in some parts of southern Sudan.

Almost all untreated victims die within one to four months. However, if treatment is received on time, some 95 percent can recover.

Medical staff at Malakal hospital, the state capital of Upper Nile, said they had received more than 70 cases in the past two weeks.

- This is an outbreak, and the numbers continue to go up - said Dr Tut Gony, the hospital's medical director, who added that many of the victims were children.

- The numbers are already unusual to be so high, and we are concerned there may be more yet to come - he said.

Some of those receiving treatment lay on plastic mats under trees in the grounds of the basic hospital, with mothers fanning away flies from the faces of their sick children.

- As long as they receive treatment in time there should be no problems in recovery, but if they are delayed in getting here then there can be serious complications - said Gony.

The doctor said that while the hospital had drugs, many found it hard to travel with roads made impassable due to rain.

MSF's Kidinda described the efforts to reach patients as a "race against time."

Outbreaks occur every five to 10 years

- In southern Sudan, where almost three quarters of the population have no access to even the most basic healthcare - Kidinda added.

Symptoms include fever, diarrhoea, vomiting, nosebleeds, a swollen spleen and jaundice.

Outbreaks occur every five to 10 years, according to MSF. The disease suppresses the immune system, leaving victims open to other infections such as malaria or pneumonia.

The outbreaks have occurred in some of the most remote regions of the south, hardest hit by a string of recent violent clashes between rival ethnic groups.

- With all the barriers facing people here -- the severe lack of infrastructure, few proper roads, crippling absence of healthcare staff and structures and the current increase in violence and insecurity in the region -- survival becomes a cruel obstacle course for those in need of life-saving treatment - said Kidinda.

More than 2,000 people have died and 250,000 been displaced in inter-tribal violence across southern Sudan since January, according to the United Nations, which says the rate of violent deaths now surpasses that in the war-torn western region of Darfur.