Sydney, Aug 29 (IANS): A pod of orcas was spotted on Thursday in waters off the coast of Sydney for the first time in six years.

The killer whales were seen chasing a group of humpback whales off the coast of Curl Curl Beach in Sydney who were on a tour on a Whale Watching Sydney boat, Xinhua news agency reported.

"There was a frenzy of activity and the orcas buzzed past the boat in formation, while chasing the humpbacks," Whale Watching Sydney said in a post on social media.

"The humpbacks were closing in together and we assume they may have been protecting a calf, but it's hard to tell with such a flurry of excitement," it said.

The tour operator said orcas' venturing as far north as Sydney is incredibly rare and that it was the first sighting of the apex predator species in Sydney waters since 2018.

According to Xinhua news agency, Vanessa Pirotta, a whale expert from Macquarie University, told Nine Entertainment newspapers that it is common for orcas to hunt juvenile humpback whales off Australia's west coast in the Indian Ocean but that it is rarely seen in east coast Pacific Ocean waters.

"The fact that we're seeing that is really interesting because that's direct evidence that we might start seeing similar behaviour to what killer whales do on the west coast," she said.