THE United States government has assured its citizens that, much like zombies, mermaids probably do not exist, saying in an official post: "No evidence of aquatic humanoids has ever been found".

"Mermaids -- those half-human, half-fish sirens of the sea -- are legendary sea creatures," read the online statement from the National Ocean Service (NOS).

The agency, charged with responding to natural hazards, received letters inquiring about the existence of the sea maidens after the Discovery Channel's Animal Planet network broadcast "Mermaids: The Body Found" in May.

The show "paints a wildly convincing picture of the existence of mermaids, what they may look like, and why they've stayed hidden ... until now", a Discovery Channel press release says.

Conversely, the US government declaration offered no conclusive proof to deny the existence of mermaids.

The statement comes after another government agency, this time the US Centres for Disease Control and Prevention (CDC), declared there was no conclusive evidence for the existence of zombies.

The CDC had published instructional materials on how to survive a "zombie apocalypse", in what the agency now calls "a tongue in cheek campaign to engage new audiences with messages of preparedness messages".

The campaign was followed by a series of cannibalistic attacks in North America.

In one such attack on May 26, a 31-year-old Miami man stripped naked and chewed off most of a homeless man's face.

The Twittersphere was suddenly alive with people talking about the real and present danger of a zombie apocalypse.

The CDC was quick to respond to allegations of corpses rising from the dead to eat the living.

"CDC does not know of a virus or condition that would reanimate the dead," a government spokesperson wrote in an email to The Huffington Post.

While zombies would be a big problem, popular folklore holds that mermaids are relatively benign creatures.

But the NOS statement associated the finned friends with more threatening mythological beasts.

"Half-human creatures, called chimeras, also abound in mythology -- in addition to mermaids, there were wise centaurs, wild satyrs, and frightful minotaurs, to name but a few," it said.