During the attack on a mosque near the South African city of Durban, killing the Imam and two other people were seriously injured, AFP reported medics. "The other two are in critical condition", said Prem Balram, a spokesperson for Reaction Unit SA, which was first on the scene.
She said the victims had their throats slit, while motive of the attack is yet to be ascertained.
The attack came shortly ahead of the Muslim fasting month of Ramadan, which begins around May 16.
"The fire department is now on the scene clearing up, the fire been extinguished", he said.
Police said the attackers remained at large after escaping in a Hyundai vehicle from the Imam Hussain mosque in Verulam town, on the outskirts of the eastern port city.
The secretary general of Jamiatul Ulama South Africa, Moulana Ebrahim Bham, told Radio Islam that they condemned the attack which "fosters nothing but tension, mistrust and insecurity within communities".
He said a third victim was attacked inside the building and jumped out of a window when it was set alight.
"The suspects have fled in a white Hyundai Getz".
According to local media, people were worshipping in the mosque in Ottawa's Old Main Road earlier this afternoon when a group of armed man stormed into the place and slit three persons' throats. Rusa is requesting the public's assistance in apprehending these suspects.
No arrests have been made at this stage and police are investigating further.
Do you have any information on the attack?
There have been some Islamophic attacks on South African mosques in the past, but few have been as violent as the one that took place Thursday.