Sharks were spotted circling near a washed up whale carcass off the coast of a popular Perth beach on Monday, prompting a warning to the public to stay away.

Several sharks could be seen metres from the shore at City Beach, swimming close to the whale, believed to be a humpback.

Despite a sign at the beach entry warning the public that sharks had been sighted and that the beach had been closed, hundreds of locals filled the beach to get a look at the enormous mammal.

Shark advice was issued after Surf Life Saving WA reported the whale carcass at about 7.30am.

A patrol boat was seen monitoring a stretch of ocean between South City Beach and Floreat Beach, with a Westpac rescue helicopter also traversing the same stretch of coastline.

A Surf Life Saving WA 4WD patrol car was also seen driving slowly up the beach to monitor the public.

The carcass could act as an attractant to sharks and see them come close to shore along the coast surrounding City Beach in the Town of Cambridge, the Department of Primary Industries and Regional Development warned.

People should “exercise additional caution”, the department said.

One local said she saw the carcass drift about 300 metres before ending up on the beach where it began emanating a strong odour that could be detected by beachgoers.

Philia Diamantidakis and Sophie Wormald were walking their dogs when they coincidentally happened upon the decomposing carcass.

“We saw that there was a very big crowd, so we were wondering what was happening, and there was a large whale at the beach with a lot of sharks,” Ms Diamantidakis said.

Ms Wormald said the shark activity would only feed people’s anxieties about swimming.

“It’s going to be unusual summer at the beach. I think people are a little bit worried, and this is not going to help,” she said.

Oscar and Lydia Moss made the trek down from Carine after seeing the carcass on the news and had been revelling in the excitement of seeing huge sharks up close.

“There was two, and they came up and tried to have a go. They’re bigger than I thought they were going to be, they look big, massive. I wanted to see some action, it’s exciting,” Ms Moss said.

“I’m actually a bit scared, but other than that, it’s pretty cool.”

Ms Moss said she would make sure to stay close to shore when swimming in the ocean from now on.

Mr Moss was less concerned.

“You’ve got more chance of dying in a car crash, don’t you? If you’re not scared to get on the road, you shouldn’t be scared to get in the water,” he said.

English tourists Millie Redshaw and Hope Collins-Wright came down from Tuart Hill to see their first experience of a whale carcass and sharks.

“We wanted to see what the fuss was about, and because we never seen a shark since living here, this is like the most exciting thing that could happen while living in Perth,” Ms Redshaw said.

“This has made our weekend, to be honest, you can tell we’re English!” Ms Collins-Wright said.

The SharkSmart website showed multiple in the area following the discovery, including a four-metre white shark at 10.46am just 10 metres offshore spotted by the Westpac helicopter.

Lifesavers spotted a 2.5 metre unidentifiable shark at 9.12am and said it was “circling” 10 metres offshore while a five metre shark was seen at 8.29am also about 10 metres from shore, heading south.

The public has been instructed to adhere to beach closures advised by council rangers, Parks and Wildlife, or Surf Life Saving WA.

Shark activity can be monitored on the SharkSmart website and any shark sightings should be reported to Water Police on 9442 8600.

DPIRD and staff from other agencies are monitoring the situation and providing advice to relevant authorities.

The shark threat comes 10 days after much loved family man Greg O’Neill, 63, was killed by a great white shark while swimming just 15 metres from shore at Sorrento Beach.