Israeli Interior Minister Eli Yishai warned on Wednesday that illegal immigrants from Sudan who do not leave the country by October 15 will be detained.
"Infiltrators from Sudan have until October 15 to leave Israel, after which date they will be placed in detention," Yishai said in a statement, adding that he had Prime Minister Benjamin Netanyahu's approval to implement such a policy.
Yishai indicated that the detention would be followed by expulsion, without going into detail on the procedure that may be followed.
He said he had "chosen to act rather than talk, in order to preserve the Jewish and Zionist character of the state for our children."
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Following a wave of arrests of illegal immigrants, Israel began expelling South Sudanese in June.
A court also gave the go-ahead for some 2,000 citizens of the Ivory Coast to be sent home.
More than 60,000 Africans are estimated to be living in Israel illegally, most of whom live in run-down neighbourhoods of south Tel Aviv.
Most are Sudanese and Eritreans who entered the country illegally via Egypt's Sinai Peninsula.
Rising tensions over the growing number of illegal immigrants exploded into violence in May when a protest in south Tel Aviv turned ugly, with demonstrators smashing African-run shops and property, chanting "Blacks out!"