Gaborone (Botswana) (AFP) - Animal campaigners demanded on Friday that a Botswana hunter's licence be revoked after an elephant was killed despite being protected, raising tensions over the country's new hunting rules.

Officials confirmed that an elephant wearing a collar -- which marks it as a protected animal -- was killed during a legal hunt in a "regrettable" incident in November.

While the hunter said the collar had not been visible and only became clear after the animal was shot, the Kalahari Conservation Society's Neil Fitt said the explanation was difficult to believe.

The government lifted a moratorium on hunting in May five years after it had been introduced, saying that certain areas would be given quotas and roughly 400 hunting licences would be distributed each year.

However, some animals remain off-limits -- including elephants with collars, as they are earmarked for scientific research.

The killed elephant was shot on November 24 in a controlled hunting area, which had been issued with an elephant-hunting quota.

"The professional hunter claimed that the collar was not visible as the elephant was in a full-frontal position," the tourism ministry said.

"Once the animal was down, they realised it had a collar on it placed for research purposes. Although this was a legal hunt, the killing of the collared elephant is regrettable."

However, Fitt said the collar was extremely large and the hunter's explanation did not seem convincing.

"The government should investigate this incident and send a strong message to professional hunters. His licence should also be revoked," Fitt said.

Department of Wildlife and National Parks said its inquiries into the incident were "at an advanced stage".

Botswana is home to over 130,000 elephants, thought to be the largest concentration in Africa.