Israel is to fly a first planeload of South Sudanese deportees to their country of origin on Sunday with more expected to follow later in the week, a spokeswoman for the Population and Migration Authority said.
"We have about 150 so far [for Sunday's flight]," Sabine Hadad told the AFP news agency on Wednesday. "We want more planes during the week."
On Tuesday, the authorities arrested 100 illegal immigrants, while another 300 people agreed to be repatriated voluntarily, she said, without saying which countries they were from.
The arrests bring the total number detained for deportation since Sunday to 240, most of them South Sudanese.
Many of the mainly African immigrants have been rounded up in the Red Sea town of Eilat, close to where they originally crossed into Israel through the porous border with Egypt.
Those who agree to leave Israel voluntarily will receive free airline tickets and a grant of $1,250, but the offer is "only on the table for one week," Haddad said.
Official figures show there are 60,000 Africans living in Israel illegally, most of whom live in run-down neighbourhoods of south Tel Aviv.
Eli Yishai, Israel's interior minister, estimates that an additional 6,000 or so may have slipped into the country undetected.
About a quarter of the total are living in Eilat, where immigration police have been stopping African passers-by and asking for identification.
"The people are very tense. It's pretty traumatic," said Jacob Berri, a spokesman for the South Sudanese community of migrants. "There are children here who only speak Hebrew. They won't even know the language where they're going."
Many of the migrants have been working in hotels and restaurants, while others have been holding down manual jobs or working as contracted day labour. All of them were technically working illegally.
Last week, an Israeli court decided that the lives of an estimated 1,500 South Sudanese were no longer at risk in their homeland, clearing the way for their mass expulsion.
|African refugees and migrant workers stand in a charity food line in south Tel Aviv, as local tensions simmer [Reuters]
The interior minister, who has frequently tried to expel non-Jewish immigrants, sparking accusations of racism, on Tuesday said the raids were "just the beginning".
"At the moment we are permitted only to deport citizens of South Sudan and the Ivory Coast," Yishai wrote in the Israel HaYom newspaper.
"The next stage is the removal from Israel of all the infiltrators from Eritrea and Sudan." He warned that allowing them to stay would mean "the end of the Zionist dream".
Rising tensions over the growing number of illegal immigrants entering Israel exploded into violence last month when a protest in south Tel Aviv turned nasty.
Demonstrators smashed African-run shops and property, chanting "Blacks out!"
Israel, which reportedly backed South Sudan through its 1983-2005 war with Khartoum, recognised the new nation and established full diplomatic relations with its government shortly after it declared independence in July last year.
The South Sudanese government was to send a delegation to Israel this week to co-ordinate the repatriation of its citizens.
Israel, a country of 7.8 million, has almost completed a high fence along the border to deter more would-be migrants who are brought to the Sinai peninsula frontier by Bedouin people-smugglers.
Newspaper reports said Prime Minister Binyamin Netanyahu had asked officials to examine whether a fence should now also be built along the border with southern Jordan, in the event that migrants try to cross the narrow Gulf of Aqaba and enter Israel.