Four African migrants were taken to an Israeli hospital with burns and smoke inhalation on Monday after a potentially deadly arson attempt on the Jerusalem building in which they were living, police said.
The incident, which police described as "very serious," took place in an old two-storey building in a poor neighbourhood near the city's Mahane Yehuda market just after 3:00 am (0000 GMT).
Police said the fire was started in a narrow entrance corridor which led to several apartments inside the building, home to 18 African migrants.
On the external walls of the building, someone had sprayed Hebrew-language graffiti reading: "Get out of the neighbourhood."
"There were 18 people living in the building, and the corridor leads to all the apartments," police spokesman Micky Rosenfeld told AFP, indicating that all the residents were of African origin.
"It is obvious that the people living there were targeted and not just the building," he said, adding that at least four people were taken to hospital, suffering from burns and smoke inhalation.
The attack took place in a small street off Jaffa Road, with the building's entrance corridor completely blackened by the fire, an AFP correspondent at the scene said, indicating it was the only entrance and exit from the apartments.
It was strongly condemned in a statement by the Israeli foreign ministry.
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"There is no justification for such a heinous crime that puts people's lives in harm's way," it said.
"Law and ethics prohibit any injury to the other, the guest and the foreigner. Jewish history compels us to take exceptional caution on these matters."
The rising number of Africans in Israel has hit the headlines in recent weeks, after a spike in racial tensions led to a riot in southern Tel Aviv, where tens of thousands of migrants live.
It happened when a protest by 1,000 people turned violent after several far-right MPs made inflammatory speeches, with one referring to the migrants as "a cancer."
Demonstrators went on the rampage, smashing up and looting African-run shops and property.
No one was injured, but police arrested 20 people on suspicion of vandalism.
Interior ministry statistics show approximately 60,000 African immigrants have entered Israel illegally. Some are refugees fleeing persecution in their home nations, but others are economic migrants.
"The issue of migrants and infiltrators from Africa is not a simple one and it requires the government to address it in the most serious and responsible manner," the foreign ministry statement said.
It said it was working with other ministries to find "solutions to the various and complex aspects arising from this issue, in coordination with international parties."