One man has succumbed to his injuries after his throat was slit when a mosque in Verulam, KwaZulu-Natal came under attack at 14:39 on Thursday.
A man died in hospital due to significant injuries, Paul Herbst from IPSS medical confirmed.
Two others remain in a critical condition.
Reaction Unit South Africa (Rusa), a private security company, said the Imam Hussain Mosque in Old Main Road in Ottawa was also set alight. The attack comes days before the start of the Islamic holy month of Ramadaan.
A video of the aftermath, showing several people on the floor in pools of blood, has since been circulated.
It is believed that the attackers are three Egyptian nationals, who allegedly slit the throats of the three people, including the imam of the mosque.
Rusa head Prem Balram said, when he arrived on the scene, he found two people outside with their throats slit.
"They were in a critical condition and bleeding profusely," he said.
Balram said another man was found inside the mosque. He said paramedics were busy attending to all three victims.
"The suspects have fled in a white Hyundai Getz. Rusa is requesting the public's assistance in apprehending these suspects. Paramedics or doctors who can assist can report to the scene," Rusa said in an earlier statement.
KwaZulu-Natal police spokesperson Captain Nqobile Gwala said police were investigating three counts of attempted murder and arson.
"They allegedly attacked three people and stabbed them. They further set certain rooms alight and fled in their getaway vehicle," she said.
"The motive of the attack on the three men is unknown at this stage."
Gwala said no arrests had been made yet.
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This is a developing story