South Africa's President Jacob Zuma has condemned acts of violence between citizens and non-nationals, his office said on Friday.
Anti-immigrant violence has flared sporadically in South Africa against a background of near-record unemployment, with foreigners being accused of taking jobs from citizens and getting involved in crime.
Citizens in Pretoria are set to march against foreigners on Friday and domestic media are reporting vandalism and acts of violence in the Atteridgeville area west of the capital.
At least 20 stores in Pretoria owned by foreigners were looted on Tuesday, but police could not confirm that the attacks had deliberately targeted foreigners.
"Many citizens of other countries living in South Africa are law abiding and contribute to the economy of the country positively. It is wrong to brandish all non-nationals as drug dealers or human traffickers," Zuma said in a statement.
"The threats and counter-threats on social media must stop," he added.
In Nigeria, 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.