Melbourne Cup contender Riff Rocket is fighting for his life after undergoing emergency surgery overnight.

The Chris Waller-trained horse was due to compete at Flemington this weekend in the Group 1 Makybe Diva Stakes over 1600m.

But the four-year-old’s racing career is on hold after Waller announced Riff Rocket underwent a colic operation on Tuesday night.

Know the news with the 7NEWS app: Download today

The horse was rushed to a vet hospital after Waller employees raised concerns.

Colic can be fatal in horses.

“Early signs are promising but the next few days will obviously be very important for his ongoing health and survival, which is our main concern,” Waller said.

“He is at the South Eastern Equine Hospital, who have done a fantastic job working through the night.

“They found the impaction in his large colon, which has been relieved, so our thanks go out to them as well as our stable vet and staff who picked up the issue early.

“Our thoughts are with the horse and his connections at this time and hopefully he will make a full racing return in 2025.”