The distant drone of engines has panicked faces scanning the sky.
People scatter as the noise draws closer. Vehicles camouflaged with mud and motor oil veer away in search of cover. The outline of a bomber appears between the clouds. "When the sound changes that's when it drops the bombs," says Mutasir Mussa, a volunteer with a local organisation documenting the attacks.
While South Sudan celebrates its independence today its former allies north of the new border in the Nuba mountains are living a nightmare.
Supply routes to the outside world have been cut, an army is massing beneath the hills and the people face a daily bombing campaign designed, locals say, to terrify them into abandoning their homes and crops.
"They are not bombing our military, they are bombing our civilians, they are terrorising our people," says Amar Amoun, a Nuban MP in Sudan's opposition. "We are asking the international community to create a no-fly zone. We are not asking Nato to come and fight a war but our people are being bombed by their own government."
Mr Amoun, who faces arrest with other Nuban leaders if he returns to the capital, Khartoum, says the bombing campaign is a deliberate tactic to "depopulate" the Nuba mountains. The green and rocky hills scattered with villages of thatched grass huts and terraced fields have witnessed generations of hardship inflicted by the Arab-led government in Khartoum.
With the division of Sudan the Nubans find themselves on the southern border of a new country whose government sees them as a threat to its control of valuable resources like arable land and oil.
The hills lie in the strategically vital state of Southern Kordofan, which will be the north's main oil-producer after the divorce from the south. The government insists its fight is with armed rebels, not villagers. Dr Ahmed Zakaria, who has been treating wards full of women and children with shrapnel wounds from the bombing, sees it differently: "We are in a battle for our survival. They want to disarm us so we will have no say in our future."
In the villages young men march in the heat of the day with sticks carved to look like rifles; in the hills women and children spend their days hiding in caves to escape the bombs; and in the fields a few farmers brave the barrage to plant crops while the rains last.
Sudan's web of internal conflicts can appear bewildering to the outside world. Since its independence in 1956, two civil wars have blighted the country and prompted the south to break away. Since 2004, the conflict in Darfur has captured the world's attention as marginalised groups have taken up arms against a central government they accuse of systematically working against them.
Sudan's oil wealth has produced a city of five-lane highways in Khartoum and wealth for the Arabs who live along the Nile; but for much of the rest of this huge and diverse country, life has been a struggle against poverty, war and exclusion.
The veteran opposition leader Yasser Arman warned the Khartoum government last week that it faces war from the "Blue Nile to Darfur" if it continues its past policies.
In the Nuba mountains, which once sheltered Africans trying to evade slavers, the people have faced repeated attempts by the central government to eradicate their culture and forcibly resettle them. The area was one of the strongholds of the rebel army, the SPLA, in its fight against the Arab-led government in Sudan's 20-year civil war.
When peace was agreed in 2005 the Nubans – a non-Arab community that has many Christians as well as Muslims – remained under the rule of Khartoum. It was hoped that elections here would give the Nubans some degree of autonomy but their candidate, Abdel Aziz al-Hilu, was defeated in what many argue was a rigged election.
In his place Khartoum appointed Ahmed Haroun, a man who like his president Omar al-Bashir is wanted by the International Criminal Court for war crimes in Darfur. The new governor moved quickly to disarm civil war veterans still loyal to the SPLA, despite international agreements that they would be integrated into the Sudan armed forces.
"After the elections we were given a final warning to evacuate the Nuba mountains," says Mubarak, a young commander with the Nuba SPLA. "But we will not go, we will stay here and defend ourselves."
Government forces have emptied the state capital, Kadugli, killing or arresting SPLA leaders and their political allies. "It is a war zone in Kadugli," says Mubarak. "They went door to door assassinating people."
Satellite images from the US-run Sentinel project have shown the northern army massing heavy weapons and troops in the towns around the mountains. But rebels have quickly established control of the mountains themselves and a long war seems in prospect. "This is our land and our home; we cannot leave this land," says the young SPLA soldier.
El-Hamra, a village about 10 miles outside Kadugli, has already been visited by the new war. It sits in the no man's land between the rebels and the government's Arab militias and army. People have fled or been killed. Stray dogs gnaw at decomposing bodies strewn around rudimentary trenches dug in the grass.
Unable to move forward on the ground the northern forces have been striking the rebel areas with MiG fighter jets and makeshift bombers converted from ageing Antonov cargo planes, as they did in Darfur.
Food supplies are running low and fields are being left unplanted, which will mean famine in the months to come. International aid workers have been evacuated, UN peacekeepers are hiding in their bases and airstrips have been bombed to prevent supplies or observers getting in.
"They are trying to make conditions here so difficult that we are forced to leave," says Mr Amoun. The struggle will continue, he says, until the government is forced to the negotiating table and the Nubans are given some measure of freedom.
"Either we get a democratic, secular Sudan where we all have rights or we get self-rule," he says. "Until then it will be a long war."
The making of a nation
*The UN Security Council unanimously approved a new peacekeeping force for South Sudan yesterday, assuring the world's newest nation military and police support to help maintain peace and security.
The council authorised the deployment of up to 7,000 military personnel and 900 international police, plus an unspecified number of UN civilian staff including human rights experts.
The council acted before independence celebrations today in South Sudan's capital Juba when the mainly ethnic African south officially breaks away from the Arab-dominated north whose capital is in Khartoum. South Sudan's independence is the culmination of a 2005 peace deal that ended more than two decades of civil war, but there are fears the conflict could be reignited because troops from the north and south are facing off in the contested oil-rich border region of Abyei. The resolution establishes a new United Nations mission in the republic of South Sudan on 9 July for an initial period of one year. It calls for reviews after three months and six months to determine if conditions on the ground will allow the military contingent of 7,000 troops to be reduced.
The UN has had a 10,400-strong peacekeeping force, known as Unmis, monitoring implementation of the 2005 north-south agreement, which operates on both sides of the border. AP