* This story has been updated:
Johannesburg - A violent protest broke out on Friday at Makro in Woodmead, according to a Thomson Reuters witness.
Employees of Makro, owned by Massmart, have been on a wage strike for a week.
Marune Rossouw, a Thomson Reuters employee, said she was trapped inside the store with around 50 other people as protesting staff rampaged through the car park, throwing stones at cars.
"We're trapped inside, in the bottles section, and the guys are outside toyi-toying (dancing)," she said by phone. "They've told us to move to the back of the store."
Massmart confirmed that a group of picketing members from the South African Commercial Catering and Allied Workers Union threw objects at the window of one of its Makro liquor stores at around 8am.
"As a result of the security protocols, approximately 35 customers and staff were confined within the store whilst arrangements were made to ensure that they could exit the site safely," a Massmart spokeswoman said.
There was no immediate comment from union officials.
Makro South Africa later tweeted: "Apologies for the disruption caused by industrial action at Woodmead Store. Normal trading has now resumed at the store."