Capt Thabo Sibuyi says the man was walking alone on Sibeko Street at about 1.50pm in Vergenoeg when the incident occurred.
The trio approached him, however as he tried to run away from them, they chased and tripped him.
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He fell to the ground and one of the men wearing a blue hoodie pointed a firearm at him, while another searched and took his cellphone and R200.
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Suspects then pushed the victim away from them and fled the scene.
A case of armed robbery has been opened at the KwaThema Police Station.
