Twin brothers have been charged with conspiring to blow up a U.S. mission and various Jewish institutions in South Africa.

Police spokesman Hangwane Mulaudzi said Monday 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.