A sinkhole the size of a backyard swimming pool has opened up in Sydney's exclusive eastern suburbs, blocking traffic, cutting power and interrupting personal training sessions.

As emergency services worked to control the spread of the hole in the harbourside suburb of Point Piper, where the prime minister lives, Kirsty Mirzikinian and her personal trainer watched in disbelief.

“Honestly I’m in shock. I’m in shock right now because I’ve come home and there’s a massive hole opposite my house,” Ms Mirzikinian told reporters on Wednesday.

“My personal trainer has come, my electricity is off and now I don’t know what to do,” said Ms Mirzikinian who was wearing her blue gym gear.

A gas line ruptured on Wentworth Street when a large part of the footpath collapsed and washed away earlier in the day after about half a month’s worth of rain pelted the city on Tuesday.

Rainwater streamed into the sinkhole, undercutting the earth underneath the road at the edge of the hole, not far from Malcolm Turnbull’s harbourfront home.

A Woollahra Council spokeswoman said a small hole was reported on Tuesday evening at the site and emergency services were called early on Wednesday as the sinkhole opened up.

Four properties on the affected side of the road were then evacuated by police.

The sinkhole has been made safe by geo-tech engineers, the spokeswoman said.

However the occupants of the home immediately affected by the hole, measuring about 15m by 3m and about 2m deep, were not at home on Wednesday, she said.

Standing in her driveway opposite the sinkhole, Ms Mirzikinian said she noticed a gas leak on Tuesday afternoon.

“We did smell a gas leak in the afternoon and the guys came and they were banging around, breaking down the concrete,” she said.

“Basically we woke up and it was like this.

“I can’t believe there’s a hole just right across the street from my house, this doesn’t normally happen.”