The incident involves Nigerian man Victor Tochukwu Nnadi, who was allegedly choked as he lay handcuffed on a main street on Thursday.
Photos and film footage taken by witnesses show a prone body with a swollen face and blood coming from his mouth.
"The barbaric behaviour of the perpetrators is not only unacceptable, but also calls for urgent attention by diplomatic authorities in Nigeria and South Africa," said Abike Dabiri-Erewa, a senior aide to the president on foreign affairs and the Nigerian diaspora.
South African police said Nnadi resisted arrest on suspicion of drug dealing and died after swallowing a dose of heroin that he was trying to sell.
A group representing expatriates, the Nigerian Union in South Africa (NUSA), complained there had been no examination to confirm he had died of heroin.
South African police say they are carrying out further investigations.
"The accused is innocent until proven guilty," NUSA spokesman Emeka Ezinteje Collins told AFP. "This is not a crime to be a Nigerian. We tend to believe that Nigerian lives don't matter to them."
According to NUSA, there are around 800,000 Nigerians in South Africa, many of them living in Johannesburg.
The community was badly hit by a wave of xenophobic violence in April 2015 that, according to an official toll, left seven people dead and thousands homeless.
In its latest report, an independent watchdog said 640 people had died from police brutality or in police custody in South Africa.
Disclaimer: No Business Standard Journalist was involved in creation of this content
You’ve reached your limit of {{free_limit}} free articles this month.
Subscribe now for unlimited access.
Already subscribed? Log in
Subscribe to read the full story →
Smart Quarterly
₹900
3 Months
₹300/Month
Smart Essential
₹2,700
1 Year
₹225/Month
Super Saver
₹3,900
2 Years
₹162/Month
Renews automatically, cancel anytime
Here’s what’s included in our digital subscription plans
Exclusive premium stories online
Over 30 premium stories daily, handpicked by our editors


Complimentary Access to The New York Times
News, Games, Cooking, Audio, Wirecutter & The Athletic
Business Standard Epaper
Digital replica of our daily newspaper — with options to read, save, and share


Curated Newsletters
Insights on markets, finance, politics, tech, and more delivered to your inbox
Market Analysis & Investment Insights
In-depth market analysis & insights with access to The Smart Investor


Archives
Repository of articles and publications dating back to 1997
Ad-free Reading
Uninterrupted reading experience with no advertisements


Seamless Access Across All Devices
Access Business Standard across devices — mobile, tablet, or PC, via web or app
