Two dogs were shot dead after killing 12 sheep at Hastings Country Park.
The attack took place on Sunday morning after two dogs from a nearby property got into the field, Hastings Borough Council confirmed.
Police and graziers attended the scene and found a number of dead sheep and others so badly mauled they needed to be shot.
The borough council, who owns the land, said in all 12 sheep died – all were in lamb.
Another 20 suffered dog bite injuries and were attended to by the vet.
In a statement, the council added: “Sunday morning saw a gruesome sight unfold at Hastings Country Park with many sheep lying dead and injured in the worst dog attack the site has experienced.”
The grazier was forced to shoot the dogs which were still attacking the sheep, the council added.
The council said it is understood the dogs belong to a resident who lives nearby.
Colin Fitzgerald, lead councillor for Hastings Borough Council’s environmental services and chair of the Hastings Country Park Management Forum, said: “This was absolutely tragic.
“We have never suffered such a devastating dog attack at the country park.
“The police are investigating to find the owners of the dogs and the reason why they were out alone.
“Everyone who has a dog should keep their dog on a lead when near any fields at the country park.”