Israeli immigration police, in their fourth day of nationwide raids to round up African illegal immigrants, had by Wednesday afternoon arrested at total of 270 people, mostly from South Sudan, officials said.
The operation, which began early on Sunday, is an attempt to track down and deport as many illegal immigrants as possible, with officials confirming that the first planeload would leave for the South Sudanese capital Juba on June 17.
"Until now, 270 illegal immigrants have been arrested, most of them citizens of South Sudan," the Population and Migration Authority said.
Since Sunday, the immigration police had been "carrying out intensive activity to locate illegal immigrants throughout Israel, with a focus on the centre and the south," it said.
Israeli figures indicate there are some 60,000 Africans in the country illegally, most of whom are living in the poor neighbourhoods of south Tel Aviv, although up to a quarter of them are living in the southern Red Sea resort town of Eilat.
Only a tiny fraction of them are from South Sudan, with rights groups putting their number at some 700, although Israeli officials say the number is at least 1,500.
Until last week, the South Sudanese were protected from deportation by a policy which afforded them "temporary protection."
But on June 7, a Jerusalem court overturned that long-standing policy, ruling that they were no longer at risk in their homeland and clearing the way for their mass expulsion.
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Earlier on Wednesday, Israel said it would fly 150 deportees back to Juba on Sunday, with more expected to follow later in the week.
"We have about 150 so far (for Sunday's flight)," Population and Migration Authority spokeswoman Sabine Hadad told AFP.
The Israeli foreign ministry confirmed that a delegation of civil servants was due to arrive in Israel in the coming days in order to help coordinate the process of repatriation.
"They are coming here to coordinate things because there isn't a South Sudanese ambassador here," said spokesman Yigal Palmor.
"There is no problem with the people who want to return of their own free will but if they don't want to cooperate, there is a need for someone to identify them," he said.
The population authority also said there had been a "sharp increase" in the number of people volunteering to return willingly in exchange for a plane ticket and a grant of 1,000 euros ($1,250) per family.
It did not give numbers, but on Tuesday, officials had said 300 people had agreed to be repatriated willingly.
Rising tensions over the growing number of illegal immigrants in Israel exploded into violence last month when a protest in south Tel Aviv turned nasty, with demonstrators smashing 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 Jewish state does not have relations with Sudan, which it has accused of serving as a base for Islamic militants.