There was a real buzz about Sydney's CBD on Friday afternoon and it wasn't just the prospect of a looming weekend.

A cloud of bees three storeys high made themselves at home during the lunch rush on Castlereagh Street, as shocked people ducked for cover.

Witnesses said the swarm were buzzing around buildings before eventually settling on a parked motorcycle, where their queen had settled.

Bystanders in the Sydney CBD had a good view of the bee swarm once it settled on a motorbike. ( Twitter: @tomeverin )

Ricky Lee works on Carstlereagh Street and said the insects were all over the road.

"It looked like a cloud of confetti," he said.

"It was three storeys high, I thought it was a ticker-tape parade.

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"There were people running on the other side of the street just trying to get out of there as quickly as they can.

"It could be seen from about two blocks away."

Beekeeper to the rescue

Vicky Brown, who runs courses in beekeeping, eventually came to the rescue after one of her students alerted her to the chaos.

"I found the queen, you find her and put her in a cage and the rest of the bees follow her inside," Ms Brown said.

The homeless queen thought to make the motorbike her new home. ( Twitter: @NSWPolice )

"They still thought she was on the motorbike for a while, it took me about an hour to put them all in a box.

"Swarms are actually quite passive, when they're in a swarm they're homeless and they feel really vulnerable and they're less likely to sting.

"Because I was crouched down low I could see her [the queen] and grabbed her and all the rest followed."

Adriana Najdanovic works nearby.

"As I walked out of the building there was this giant cloud of bees, but no one knew what it was until we of closer," she said.

"It was like across the building.

"It went up towards Park Street but the swam went up a couple of floors."