Sudan\'s parliament passed a law on Wednesday cancelling the Sudanese nationality of southerners, four days after their homeland declared independence from the north, state media reported. \"All the southerners are going to lose their Sudanese nationality directly\" because of the amendments to a law approved by parliament, MP Ismail al-Haj Musa told AFP, confirming a report on the official SUNA news agency. Despite a mass migration back to the south since October -- some 360,000 are already thought to have returned -- more than one million southerners remain in the north, according to the UN refugee agency UNHCR. Many of those remaining were born in the north. Under the amendments, which await a final reading next Monday, \"Sudanese nationality is automatically cancelled for any person acquiring the nationality of the state of South Sudan,\" SUNA said. Musa, who belongs to Sudan\'s ruling National Congress Party, explained that, due to the registration for January\'s independence referendum, in which southerners voted overwhelmingly to split with the north and forge their own nation, the national identity of southerners had been established. More than 99 percent of those voting in the south opted for independence. But only 58 percent of southerners in the north did so, with many concerned about the implications of secession for their work and residency status. Prior to southern independence last Saturday, the Khartoum government had already ruled out the possibility of dual nationality for southerners remaining in the north, and dismissed all those working in the public sector. \"For the southerners that want to work in the private sector in the north, they will have to get permission and residency permits,\" Sudan\'s top presidential aide, Nafie Ali Nafie, said at the end of last month. But he also said there would be a nine-month transitional period, allowing them \"to settle their situations.\" Millions of southerners fled to northern Sudan during the devastating north-south civil war between 1983 and 2005 that left their region in ruins, most of them to Khartoum. Many have returned south this year to participate in the building of their new nation. But the UNHCR has warned that lack of clarity over the future rights of southerners in the north, including on work and property ownership, together with hostile comments by Sudanese officials, had accelerated the exodus. \"This (situation) is very difficult and very traumatic... There is a lot of anxiety out there,\" the UNHCR\'s Sudan representative Peter de Clercq told AFP last week. He said the Khartoum government had sent out some reassuring messages but nothing concrete and there had also been some \"very unpleasant messages.\" This had provoked a rise in the number of southerners leaving their homes in Khartoum and moving to makeshift staging posts like railway stations and river ports, he added.