One was beheaded and left on a seashore with a driftwood cross topped with the body of a dead seagull.
And a pregnant mare was discovered mutilated in a field. She was treated by a vet but died after her foal was stillborn.
The two attacks happened close to the time of the current “supermoon”.
The beheaded horse was identified on Pentewan beach close to Mevagissey, Cornwall, on Bank Vacation Monday with “Rest in Peace” written in the sand beside it.
The other was discovered close to Gainsborough, Lincs.
The killings come after a stallion called Eric was found dead in Cornwall with his right eye gouged out, teeth eliminated and genitals hacked off.