He said paramedics were busy attending to all three victims.
IPSS Medical Rescue's Paul Herbst said: "IPSS can now confirm that the person with the slit throat unfortunately has passed away in hospital".
Map locating Verulam in South Africa, where a mosque was the target of an attack.
According to police spokesperson, Captain Nqobile Gwala, at around 2pm, three men entered the Imam Hussain Mosque situated along Old Main Road after prayer. The two others remain in a critical condition. The imam was in a critical condition.
"The local people here identified them", Balram said.
Rusa said in a statement: "The suspects have fled in a white Hyundai Getz".
The motive of the attack was not clear but the three suspects, who fled in a white vehicle, had been identified as Egyptian, he added. He was treated by paramedics on the scene and transferred (to hospital).
Private security company Reaction Unit South Africa's Prem Balram said: "Upon arrival‚ Reaction Unit officers found that two victims had their throats slit and were bleeding profusely. One knife was left behind", Balram told AFP.
He said a third victim had been attacked inside the building, which was then set alight, and had jumped up of a window.
South Africa has a history of relative religious tolerance.
The attack came a day before the start of the holy month of Ramadaan. "Speculation about the motive is quite risky at this point".