The gunmen first opened fire on customers outside the bar before continuing the attack inside. They also set two vehicles on fire before fleeing the scene.
Deputy provincial police commissioner Maj Gen Fred Kekana told AFP news agency that the attack may have been a retaliation for an incident last month in which one person was killed and another wounded.
Speaking at the scene, Kekana said police had clear pictures and, in some cases, names of the suspects. No arrests had been made by Sunday morning.
Ten killed in Cape Town shooting
Hours later, another mass shooting took place in the early hours of Sunday morning outside an entertainment venue in a township near Cape Town.
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Ten people were killed and 11 others were injured in the shooting. Five victims died at the scene, while another five died in hospital.
Police had not indicated a motive for either attack, and no arrests had been made in either case by Sunday morning.
The two shootings came days after 11 people were killed in Durban when gunmen stormed a house in the KwaMakhutha township.
South Africa struggles with gun violence
South Africa has one of the highest murder rates in the world, with illegal weapons widely available and about 60 murders recorded every day in the country of 62 million.
Gun violence has remained a persistent problem for decades, while recent mass shootings have raised concerns that the situation is worsening. Much of the violence is linked to turf wars between gangs involved in drug trafficking and illegal mining.
In February, President Cyril Ramaphosa called organised crime "the most immediate threat to our democracy, our society and our economic development".
Earlier this year, the military was deployed alongside police in areas with the highest murder rates in an effort to reduce armed violence.
The latest shootings also come as authorities investigate a series of killings in Ekurhuleni, east of Johannesburg. On Saturday, a tenth woman's body was found in the area. Local police said they were unable to rule out a serial killer operating in the area, citing similarities between the deaths.