* Nigerians target South Africa's MTN in revenge attacks
* Anti-foreigner violence hit Pretoria this week
* High unemployment fuels South African xenophobia (Recasts with ultimatum from youth body, adds South Africa foreign ministry comment)
By Paul Carsten and Anamesere Igboeroteonwu
ABUJA, Feb 23 (Reuters) - Nigerian protesters on Thursday demanded that South African citizens and businesses leave the country and vandalised the head office of mobile phone giant MTN in Abuja in retaliation for anti-Nigerian violence in South Africa.
The National Association of Nigeria Students (NANS) said it had given South Africans 48 hours to get out otherwise the attacks would continue and the vandalisation of MTN's offices would be just the beginning.
Nigeria and South Africa, the continent's two largest economies and pre-eminent diplomatic and military powers, have a volatile relationship.
The students' threats follow the looting this week of at least 20 small businesses believed to belong to immigrants in South Africa's capital, Pretoria.
"We are not going to kill like them and that is why we have asked their citizens to leave, but we will sure destroy their businesses," NANS president Aruna Kadiri told Reuters.
Nobody was killed in the violence in Pretoria, according to South African police.
South African foreign ministry spokesman Clayson Monyela called for both sides to keep their cool.
"'An eye for an eye makes the world blind' .... 'Violence begets violence'. We are better than this. Africans are one people!" Monyela said on Twitter.
A spokesman for MTN, the biggest South African company active in Nigeria, said protesters stormed the regional head office, vandalising equipment, attacking customers and stealing some of their phones.
A Reuters reporter could see no obvious damage from the outside of the building which had been cordoned off.
"They forcefully entered the MTN office. Security men were around but unable to curtail the protesters, who forced the gates open and entered the office," said one witness, adding that students and petty criminals appeared to be among the mob.
The incident coincided with a visit by MTN chairman Phuthuma Nhleko to the Nigerian capital to see Vice President Yemi Osinbajo, who has been in charge for the last month with President Muhammadu Buhari absent on sick leave.
Earlier this week, Nigeria's foreign ministry said it would summon South Africa's envoy to raise its concerns over "xenophobic attacks" on Nigerians, other Africans and Pakistanis.
South African police have refused to say if the Pretoria attackers were specifically targeting foreigners. But South Africa's Home Affairs Minister Malusi Gigaba on Thursday acknowledged there had been renewed violence against foreigners this year.
"Unfortunately, xenophobic violence is not new in South Africa," Gigaba said.
The violence against immigrants has flared against a background of near-record unemployment, with foreigners being accused of taking jobs from locals and getting involved in crime.
The minister said some residents in Pretoria planned a march on Friday against immigrants. (Reporting by Ed Cropley in Johannesburg, Chijioke Ohuocha in Lagos, Paul Carsten in Abuja, Wendell Roelf in Cape Town and Anamesere Igboeroteonwu in Onitsha; Writing by Ed Cropley and Ulf Laessing; Editing by James Macharia and Richard Lough)