A Sydney council says its parks staff are on "high alert" after a local dog was poisoned by rat bait hidden inside meat at a popular inner-west dog-walking spot.

In a post to her Facebook page, Rozelle resident Lily Kenny said she was walking her dog Lola at a grassed reserve on the Bay Run at Lilyfield on Monday when the greyhound ingested a large amount of rat poison that had been "purposely planted in a local oval by some horrible person".

"It breaks my heart that people can be this horrible and heartless," she wrote in the post which has since received thousands of comments.

"I really hope no other dogs were affected by this, but please be cautious guys!"

Inner West Council Mayor Darcy Byrne said he was angry, disappointed and disgusted by the incident.

Dogs have now been poisoned near Le Montage at Rozelle and Pioneers Park in Leichhardt.

Mr Byrne said council staff searched both sites early this morning but found no further baits.

"All of council's parks staff are on high alert to look out for any further baits in any inner-west parks," he said.

"We ask the public to be on the lookout as well."

Mr Byrne said council is helping the RSPCA with an investigation.

"We will not tolerate this sort of criminal behaviour in our community."

Ms Kenny told the ABC she regularly walked Lola at the grassed reserve between Perry Lane and Church Street in Rozelle and had done twice on Monday.

During their afternoon walk she noticed Lola eat what appeared to be a piece of cooked mince with a green pellet inside.

She feared the four-year-old rescue dog had ingested more on their morning walk.

"I was terrified. I completely freaked out and made sure I got to the vet as quickly as I could," she said.

The vet induced vomiting and told her it was likely Lola would recover completely but it had been a close call.

"She had so much in her body the vet asked me if she had gotten into a packet of them," Ms Kenny said.

She later returned to the park and found another five balls of mince filled with pellets.

"I just can't believe someone would do such a thing," she said.

"If I hadn't noticed that small pellet she could have died.

Lily Kenny returned to the park and collected several more pieces of meat which contained the pellets. (Supplied: Facebook)

"I am just completely shocked that this could happen in such a dog-friendly area.

"She is my everything and I honestly don't know what I would do if anything happened to her."

Ms Kenny planned to place posters on the Bay Run warning other dog owners to beware.

'They bleed internally'

Rat poison acts as an anti-coagulant, causing internal bleeding if ingested. (Supplied: Facebook)

Haley Weston, a vet nurse at a Sydney after-hours veterinary emergency service, said owners who suspect their pets have been poisoned should bring the animal in for treatment within 30 minutes, if possible.

"Rat bait is an anti-coagulant which means it prevents the blood from clotting so they can start bleeding internally," she said.

"Rat poison starts affecting the animal by breaking down their organs.

"The longer it's in their system, the worse the effects on their body."

She said dogs were often treated with Vitamin K, which is an effective antidote.

Ms Weston said she had not seen many cases of baiting at the Camperdown practice due to the large number of apartments in the area.

However when she worked at a vet in the western suburbs she saw it "quite a bit".

"It is mostly angry neighbours or people fed up with dog parks or dog beaches," she said.

"It's easier for someone to throw baited food over the fence of their backyard so I saw it a lot there."

She advised owners to bring the baited food to the vet for testing to determine the exact poison used.