JOHANNESBURG (AP) — South Africa has closed its diplomatic missions in Nigeria, underscoring the growing strain between Africa's two largest economies after the latest wave of xenophobic violence in South Africa., the Department of International Relations and Cooperation said Thursday.

The department said while there had been "no direct physical threat" to any diplomats or staff, the situation remained "somewhat unpredictable" and there were sufficient safety concerns to close the offices in Lagos and Abuja on Tuesday.

On Sunday, violent mobs began looting and setting fire to foreign-owned businesses in several areas of Johannesburg and the South African capitol Pretoria. The unrest lasted for four days, with at least five people killed and more than 250 people arrested.

Outbreaks of violence against Nigerians and citizens of other African nations have regularly erupted in South Africa in recent years, with some South Africans accusing foreigners of peddling illegal drugs or taking jobs when official unemployment is nearly 30 percent.

The latest wave incensed Nigerian citizens and officials alike, with Nigerian Minister of Foreign Affairs Geoffrey Onyeama calling the latest attacks "sickening."

Nigeria subsequently recalled its High Commissioner to South Africa and boycotted a meeting of the World Economic Forum on Africa that is underway in Cape Town this week.

Nigerian airline Air Peace also offered to fly Nigerians wanting to leave South Africa back home, free of charge, on Friday.

South-African owned businesses in Nigeria have faced a wave of retaliatory violence, with branches of South African telecommunications giant MTN and supermarket chain Shoprite attacked and looted in several Nigerian cities.

Nigerian police say security has been ordered for foreign missions, foreigners and their businesses across Nigeria.

International Relations and Cooperation Minister Naledi Pandor said on Thursday that Nigeria needs to address the fact that some Nigerians are, in fact, involved in criminal activities in South Africa.

"This kind of assistance of ensuring such kind persons don't come to our country would be of great assistance to our nation," Pandor told local news station eNCA.

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Olukoya reported from Lagos, Nigeria.