The owner of the two BP service stations at West Wollongong says "cocky" bandits brandishing guns, knives and axes have bailed up one of his service stations five times in two months.

The latest robbery, on Tuesday, in which cash and cigarettes were stolen and an attendant was threatened with a kitchen knife, was the last straw for the owner, who did not want to be named.

"They wear plastic face masks and hoodies, and charge in," he said. "They've put attendants, even customers on the floor. One attendant has been held up twice."

The owner runs both BP service stations on either side of Crown Street at West Wollongong.

He said the store on the southern side, with an attached newsagent, had been the target of the robberies. He called the robbers "cocky", saying hold-ups occurred even with customers inside the store or filling up petrol.

"The workers don't want to come to work, and won't go outside at night," he said.

"One was outside cleaning at night, and got a knife held in his back."

The stores' manager said she was also fed up with the frightening incidents.

"When your staff are put on their knees with an axe behind their head, or as guys run behind the counter with a 40-centimetre blade, it's time to do something," she said.

"These guys don't care. We've had people in the store, or filling up petrol, and they still come."

Both service stations will soon alter their opening hours. The south-side store, now open 24 hours, will close at 11pm. The opposite store, which closes at 11pm, will switch to a 24-hour operation.

The owner said he would also install new security cameras and employ a new security company.

Anyone with information on the robberies should contact Wollongong police or Crime Stoppers.