Twin brothers have been charged with conspiring to blow up a US mission and various Jewish institutions in South Africa.
Police spokesman Hangwane Mulaudzi says that Brandon-Lee Thulsie, Tony-Lee Thulsie and two other people who are yet to be charged were arrested in Johannesburg on Saturday.
The four were arrested before boarding a flight to Syria and had been under surveillance for nearly a year.
A provisional charge sheet says the brothers may have links to the Islamic State group.
The brothers will have the opportunity to apply for bail on July 19.