"Sudan is four countries ... No, no Sudan should be just one...," the voice of the local singer in a southern language came loud and noisy from the old tape recorder next to Sonta as she sat sweating in the searing sun at the make shift bus-station in Amarat district in southern Khartoum.

The 20-year-old woman from Warrap state and her cousin were sitting on a heap of old furniture along with hundreds of other southerners, waiting to be transported to southern Sudan.

They have left their homes around Khartoum and they have been here for nearly a week waiting for the buses to come.

A one-year-old baby girl with a dusty face and shabby clothes was nibbling at a poorly baked portion of flour soaked in meat sauce.

It's very clear that these people have been suffering for years and that they are now taking serious troubles to go back to their ancestral homeland. Sonta was born in Khartoum but she's yearning to "return home" she says.

But what about those words in the song beside her? Why did she choose to listen to that particular song?

"Ah, it's because we would like Sudan to remain united,” she replied.

"So why are you leaving the north now, at this particular moment, just one month before the referendum that may lead to the secession of the south?" I asked.

She just giggled by way of an answer. Her confusion reflected that of many southerners displaced in the north who feel torn apart between two contradictory choices.

Many of the nearly two million southerners living in the north have acquired a certain level of social and economic stability.

They were granted land plots to build homes and sent their children to schools and universities.

They found relatively secure jobs or engaged in commerce. The entire new generation under 30 were born in Khartoum and they speak Sudan's Arabic dialect with a northern accent.

But there's a large chunk of displaced southerners who remained in limbo. They live in moth-eaten slums with basically no basic facilities whatsoever. These make up the bulk of the present wave of returnees.

However there's another important factor in play. Southern-based relief organisations and Sudan People's Liberation Movement (SPLM) affiliated NGOs have allegedly been giving handsome amounts of money to every family that agrees to return to the south.

These amounts, I'm told, can reach $3,000. This would tempt any family that lives on $1 to even $10 a day to take the bait.

But in some cases it turns out it's the NGO that finally takes the bait, as many of those who go to the south sneak back to Khartoum later after they have pocketed the money.

But in reality, southerners in the north are divided.

Those who obtained some economic and social benefits in the north generally prefer to stay in the north for the moment. The future in the south is uncertain to them so far.

This situation has been reflected in the voter turn-out throughout the three weeks registration process.

Out of up to two million displaced southerners in Khartoum, only about 100,000 have showed up to register.

The SPLM has been successful in convincing many of them not to register or vote in the north, warning them of pressure and manipulation by the Sudanese government in order to influence their choice. 

And the choice of time for the organising of the current major campaign of "voluntary return" has created a clear distraction because it "coincided" with the registration period.

If a southern family is going to return to the south then they don't need to, and can't even, register in the north. By the time they reach the south the registration period is over.

Just as the case is with Sonta, many displaced southerners do not seem to grasp the long-term implications of what's about to befall Sudan as they know it.

Even though they are displaced, life has so far been a bit easy because it involved potential choices.

Had they wanted to return to the south a long time ago they could have done so. But now if Sudan is split there's no agreement so far between the two peace partners about what kind of status these people should have.

Earlier this year the government in Khartoum announced that if southerners chose to secede then those two million of them living in Khartoum will automatically lose their citizenship status and they won’t have the right to avail by social services in the north. They will have just one option: to leave.

Later on the government amended that decision and said those who choose to stay in the north may be welcomed in the north. But until now it’s not exactly clear what status they will have.

Will they be considered legal refugees with limited rights? Will they be granted a dual citizenship, which is certainly what they prefer most?

Or will they have to forget about the south and accept to remain in the north as a black-African ethnic minority, yet a smaller minority living in a majority Muslim, Arab north?

Wasn't this the very situation that originally led to decades of civil in Sudan?

And even some southerners who were never displaced and who live in the south are facing some hard choices.

For instance there's a sizable Muslim minority in the south. They are ethnically black African, belonging to the same tribes there.

But because of their religion they prefer Sudan to remain united so that they don't turn into an even more vulnerable minority.

Mohamed Carlos, 31, is one of them. He's a tribal Sultan from South Blue Nile State and strongly supports unity.

I met him at a registration centre and he says he thinks pro-unity southerners are more numerous than it appears.

They also need not to give up even after the south splits. According to him they can be "instrumental in reuniting Sudan one day".