Both have dual British and South African citizenship and live in Cape Town, according to The Telegraph.
Despite previous attacks on tourists in South Africa, no similar warning was issued by the Foreign Office with regards to terror.
The British foreign office confirmed that a pair of Britons had been kidnapped and warned of a heightened risk of attacks by "terrorists" in South Africa.
And police probing their disappearance in KwaZulu-Natal province unearthed disturbing links to an alleged ISIS cell.More news: Royal Bank of Canada (RY) Earning Somewhat Positive Media Coverage, Analysis Shows
Although the couple are still missing, two suspects have been arrested and have been named as Sayfydeen Aslam Del Vecchio and Fatima Patel, according to the Hawks Police Unit.
But officials in South Africa criticised the Whitehall comments, including the director of southern Africa operations at the Terrorism Jasmine Opperman, who said that the update on travel advice was "alarmist".
"The main threat is from extremists linked to Daesh (formerly referred to as ISIL)".
Police in South Africa have revealed they are still searching for a British couple who were kidnapped a week and a half ago.More news: Chevron Corporation (NYSE:CVX) - P/E and PEG Value Under Consideration
Our travel advice already states that terrorists are likely to try to carry out attacks in South Africa.
Some time last week, this couple - whose names have not been released yet - somehow crosed paths with a nefarious group that either kidnapped them, is holding them against their will or have done worse.
"There's also a threat from individuals who may have been inspired by terrorist groups, including Daesh", it added.
Similar travel advice was given in 2016, with both the United Kingdom and the U.S. warning of the possibility of terror attacks on upmarket shopping areas and malls in Johannesburg and Cape Town.More news: Wal-Mart Stores' (WMT) "Outperform" Rating Reaffirmed at Telsey Advisory Group
The country has so far been spared the jihadist attacks that have struck several other countries on the continent.