The first group of South Sudanese refugees were airlifted to Juba from Khartoum on Monday.

A total of 164 people arrived in South Sudan's capital city, and some 15,000 more will be moved from the Kosti refugee camp in the White Nile State to Khartoum, where they will board southbound planes by May 20.

The flights from Khartoum to Juba will continue on a daily basis, AllAfrica reported.

Two civil wars in Sudan and South Sudan's subsequent independence last July have left many ethnic southerners on northern soil. Nearly 500,000 southerners lost their citizenship after the split, according to the BBC, and recent border clashes and the looming threat of all-out war have put many of these refugees in danger.

With bombing raids continuing and negotiations over oil contracts still stalled, Sudan's government declared last month that the refugees in Kosti represented a security threat, and ordered their evacuation. Although the refugees are considered southerners, many of them have never been to South Sudan, leading the International Organisation for Migration, which is helping to coordinate the move, to fear that the program could turn from a humanitarian initiative into a forced deportation.

If the May 20 deadline is enforced, this becomes a deportation and we will not have any part in it, IMO Sudan director, Jill Helke, told AFP.

It is my first time to the South. I was born here in Sudan, Cecilia Peter, a teacher who was one of thousands of southerners who have been fired from their jobs in Sudan in the past year, told the BBC.

Hundreds of thousands of people have already fled to South Sudan in response to an earlier Sudanese decree that southerners must either formalize their status or leave, and more moved south in response to the independence. There are also about 80,000 Sudanese  living in South Sudan.