In the single functional hospital in war-ravaged South Sudan's Upper Nile region, the only X-ray machine is broken, the sole surgical theatre is lit by a single light, and electricity is provided by generators that often break down.

Key points: Evan Atar Adaha is the only doctor in the only surgical hospital in Upper Nile

Evan Atar Adaha is the only doctor in the only surgical hospital in Upper Nile Civil war has raged since 2013 in a country with just 120 doctors to 12 million people

Civil war has raged since 2013 in a country with just 120 doctors to 12 million people The UN has awarded Dr Atar the Nansen Refugee Award for his life-saving work

But a team of medical staff led by head surgeon Evan Atar Adaha works tirelessly to treat all those in need, regardless of their background, at Maban Referral Hospital, which serves more than 200,000 people.

While most surgeons work hard, Dr Atar's schedule is punishing: to meet demand, he has been known to work 48-hour shifts, living in a canvas tent near the hospital, far from his family in Kenya.

He only sees his wife and their four children three times a year.

Sorry, this video has expired South Sudanese doctor wins prestigious UN prize

Dr Atar was recognised today with the Nansen Refugee Award from the United Nations refugee agency, and was modest about his personal sacrifice, telling the ABC's World program it's "difficult" but "we have to adapt".

"Our work as a doctor is to save lives and [provide] ease for those who are sick — that is why we are committed," said Dr Atar, who is also the medical director of the hospital, in the town of Bunj.

Sudanese refugees and patients rest at the Maban hospital. ( Supplied: UNHCR/Will Swanson )

South Sudan, the world's newest nation, has been wracked by civil war since December 2013.

The country had just 120 doctors and 100 nurses to care for 12 million people at independence in 2011, according to the UN, but that number dropped as medical workers fled the violence or were killed.

Healthcare providers have been routinely targeted during the conflict — including in Maban county, where "Dr Atar's Hospital", as it's often called, is located.

Dr Atar did not stop working even when aid organisations in the area were attacked and several of his medical staff were forced to leave.

The hospital conducts between 15 to 20 caesarean section delivery procedures each week. ( UNHCR/Will Swanson )

His 20-year commitment to treating war-affected people began with a volunteer position in Sudan's Blue Nile state, where he established a hospital in the midst of armed conflict.

"The war was tense and the aerial bombardment was there but we started because the civilians were caught in the situation and we have to try and give them the services," he said.

As the violence escalated in 2011, he made the tough decision to flee, taking his staff and all the medical supplies they could transport across the border to South Sudan.

Now, Dr Atar and his team treat thousands of patients a year, many of them refugees from Sudan's Blue Nile, as well as internally displaced South Sudanese.

The hospital is in desperate need of basic equipment such as theatre lamps, oxygen and generators, while mothers often have to share beds in the maternity ward.

And the UN expects another 12,000 refugees will arrive before the year is out.

Hospital patient and refugee from Sudan Gisma Al Amin sits with her newborn baby in the maternity ward. ( UNHCR/Will Swanson )

"What we need is … peace. This is the only thing that can actually reduce our work — peace in South Sudan and peace in Sudan," Dr Atar said.

That, he said, "Will bring us rest".