The animals, both adult males, were strung up by their necks from a first floor window grill in the Kensington area of Liverpool on Monday.

It is not yet known whether they died before being hanged, or as a result of it. On Tuesday the RSPCA described the incident as "horrific".

Spokeswoman Heather Holmes said: "Whoever did this was obviously determined to cause maximum distress."

Empty flat

She added: "That in itself is sickening, before you even begin to think whether they killed the cats first or hanged them and watched them die.

"However you look at it, it is absolutely horrific."

A spokeswoman for Merseyside Police said the cats were hanging from the window of an empty flat.

Police and the RSPCA appealed for anyone with information about the incident to get in touch.