The National Immigration Authority's Oz unit has overseen the departure of 800 illegal migrants from Israel since becoming active three weeks ago, the Interior Ministry announced on Thursday. Seven hundred people left the country of their own will, and a 100 were deported, the ministry added. The Oz unit has checked 4,000 foreign citizens since coming into operation. Six hundred of those were detained and 400 were arrested. Around 50 Palestinians have been expelled from Israel. "Flights for 90 additional deportees are being arranged." Earlier this week, the Oz unit came under fire from an NGO which said 64 percent of people being detained were African asylum-seekers who cannot be expelled. The Hotline for Foreign Workers said refugees from Eritrea and Sudan were being arrested for breaching the "Gadera to Hadera" ban which prohibits them from entering the Central region. Yohanis Bayo, co-founder of the African Refugees Development Center in south Tel Aviv, confirmed that many African refugees were being targeted by the unit. "Yesterday's arrests at the Sheraton Hotel in Tel Aviv is an example of this. The majority of these people were refugees," he told The Jerusalem Post on Thursday. "Many of the asylum-seekers don't know what to do. They've been asking me what to do, but there is no answer," he added. "The activities of the Oz unit are affecting the refugees hugely." "It's like a revolving door. The refugees have been given papers by the government, but then they're arrested," he said. "It is unimaginably difficult." Sabin Hadad, spokeswoman for the Oz unit, said in response, "We are not targeting any specific group. The African refugees cannot be deported. We are making sure they are staying out of the Gadera-Hadera zone." Hadad said the African migrants were being kept south of Gadera and north of Hadera "instead of being in prison. They know there are [Oz] operations in Tel Aviv and it's not legal for them to be there." If caught by the unit, the migrants must commit to not returning to central Israel, or remain in prison, Sabin added. "Of course, this does not apply to the 600 recognized asylum-seekers in the country." In its statement. the Oz unit said, "Undercover and open operations are under way, while we also maintain a presence across the large cities." Phone calls from members of the public to a special hot line have also been received, the unit said. The Oz unit has also targeted businesses which illegally employ foreigners, such as restaurants and hotels. More than 40 businesses have had files opened against them for employing illegal migrants. If caught, business owners face thousands of shekels in fines. Repeat offenders are referred to the courts system.