A bid to free five elephants from a Colorado zoo has been rejected after a court ruled elephants are not people.

An animal rights group argued Missy, Kimba, Lucky, LouLou and Jambo were effectively imprisoned at the zoo, and had filed to have them moved to an elephant sanctuary.

It tried to bring a habeas corpus claim on behalf of the animals - a legal process which allows a person to challenge their detention in court.

The Colorado Supreme Court said the matter boiled down to "whether an elephant is a person" and therefore had the same liberty rights as a human - ultimately deciding that they did not.

It ruled 6-0 in favour of a previous district court decision that said the state's habeas corpus process "only applies to persons, and not to nonhuman animals".

This was true "no matter how cognitively, psychologically, or socially sophisticated they may be," State Supreme Court Justice Maria Berkenkotter added in her ruling.

While she said the five elderly African elephants were "majestic," the court ruled the claim could not be brought "because an elephant is not a person".

The Nonhuman Rights Project (NRP) petitioned for the elephants to be moved from Cheyenne Mountain Zoo to a "suitable elephant sanctuary" in 2023.

The group argued the animals had a right to freedom because they were emotionally complex and intelligent animals.

It claimed the elephants showed signs of "trauma, brain damage, and chronic stress" and that they were effectively "imprisoned" at the zoo.

Cheyenne Mountain Zoo rejected the claim, arguing the elephants had received remarkable care, and was supported by a district court.

After the Supreme Court ruling, Cheyenne Mountain Zoo called NRP's lawsuit "frivolous" and said it had "wasted" time and money on the case.

It accused the group of "abusing court systems to fundraise" and claimed its goal was "to manipulate people into donating to their cause by incessantly publicising sensational court cases with relentless calls for supporters to donate".

NRP said the decision "perpetuate[d] a clear injustice, stating that unless an individual is human they have no right to liberty".

"As with other social justice movements, early losses are expected as we challenge an entrenched status quo that has allowed Missy, Kimba, Lucky, LouLou, and Jambo to be relegated to a lifetime of mental and physical suffering," the group said in a statement.

An earlier bid by NRP to free an elephant named Happy from New York's Bronx Zoo was rejected after the court judged she was not legally a person.